diff --git a/doc/source/package-ref.rst b/doc/source/package-ref.rst
index 5fe98ccb7..cc3bec05f 100644
--- a/doc/source/package-ref.rst
+++ b/doc/source/package-ref.rst
@@ -167,6 +167,35 @@ get_current_placement_group
 
 .. autofunction:: ray.util.placement_group.get_current_placement_group
 
+.. _custom-metric-api-ref:
+
+Custom Metrics APIs
+-------------------
+
+Metric
+~~~~~~
+
+.. autoclass:: ray.util.metrics.Metric
+   :members:
+
+Count
+~~~~~
+
+.. autoclass:: ray.util.metrics.Count
+   :members:
+
+Gauge
+~~~~~
+
+.. autoclass:: ray.util.metrics.Gauge
+   :members:
+
+Histogram
+~~~~~~~~~
+
+.. autoclass:: ray.util.metrics.Histogram
+   :members:
+
 Experimental APIs
 -----------------
 
diff --git a/doc/source/ray-metrics.rst b/doc/source/ray-metrics.rst
index c6137ac38..cac3308cf 100644
--- a/doc/source/ray-metrics.rst
+++ b/doc/source/ray-metrics.rst
@@ -1,9 +1,10 @@
-Ray Monitoring with Prometheus
-==============================
+Ray Monitoring
+==============
 To help monitoring Ray applications, Ray
 
 - Collects Ray's pre-selected system level metrics.
 - Exposes metrics in a Prometheus format. We'll call the endpoint to access these metrics a Prometheus endpoint.
+- Support custom metrics APIs that resemble Prometheus `metric types <https://prometheus.io/docs/concepts/metric_types/>`_.
 
 This page describes how to acces these metrics using Prometheus.
 
@@ -151,3 +152,11 @@ Now, modify a Prometheus config to scrape the file for service discovery.
         - '/tmp/ray/prom_metrics_service_discovery.json'
 
 Prometheus will automatically detect that the file contents are changing and update addresses it scrapes to based on the service discovery file generated by Ray.
+
+Custom Metrics
+--------------
+Ray supports custom metrics APIs to enable developers to have visibility to their applications.
+
+It current supports 3 metric types. All metric types have the same definition as `Prometheus metric types <https://prometheus.io/docs/concepts/metric_types/>`_.
+
+:ref:`Custom Metrics APIs Package Reference <custom-metric-api-ref>`
\ No newline at end of file
diff --git a/python/ray/experimental/metrics.py b/python/ray/experimental/metrics.py
deleted file mode 100644
index db7079828..000000000
--- a/python/ray/experimental/metrics.py
+++ /dev/null
@@ -1,38 +0,0 @@
-from ray._raylet import (
-    Count,
-    Histogram,
-    Gauge,
-    Sum,
-)  # noqa: E402
-"""Metric/Stats module for worker.
-
-This module is responsible for providing four classes mapping from stats of
-cpp.
-
-How to use:
-  For Count, Gauge and Sum, we may define a metric like this following:
-    gauge = Gauge(
-      'ray.worker.metric',
-      'description',
-      'unit',
-      ['tagk1', 'tagk2']).
-  The last parameter is default tag map. You can use gauge.record(1.0) with
-  default tags or gauge.record(1.0, {'tagk1', 'tagv1'}) that means the tagk1
-  is updating in tagv1.
-
-  It's addtional boundaries to Histogram measurement,
-    histogram = Histogram(
-      'ray.worker.histogram1',
-      'a', 'b', [1.0, 2.0],
-      ['tagk1'])
-
-  Recommended metric name pattern : ray.{component_name}.{module_name}, and
-  name format must be in [0-9a-zA-Z].
-"""
-
-__all__ = [
-    "Count",
-    "Histogram",
-    "Gauge",
-    "Sum",
-]
diff --git a/python/ray/includes/metric.pxi b/python/ray/includes/metric.pxi
index 443a476ad..ba89ba840 100644
--- a/python/ray/includes/metric.pxi
+++ b/python/ray/includes/metric.pxi
@@ -50,7 +50,8 @@ cdef class Metric:
         # Default tags will be exported if it's empty map.
         if tags:
             for tag_k, tag_v in tags.items():
-                c_tags[tag_k.encode("ascii")] = tag_v.encode("ascii")
+                if tag_v is not None:
+                    c_tags[tag_k.encode("ascii")] = tag_v.encode("ascii")
         c_value = value
         with nogil:
             self.metric.get().Record(c_value, c_tags)
diff --git a/python/ray/serve/backend_worker.py b/python/ray/serve/backend_worker.py
index c8e188f15..d686c30f5 100644
--- a/python/ray/serve/backend_worker.py
+++ b/python/ray/serve/backend_worker.py
@@ -12,7 +12,7 @@ from ray.async_compat import sync_to_async
 from ray.serve.utils import (parse_request_item, _get_logger, chain_future,
                              unpack_future)
 from ray.serve.exceptions import RayServeException
-from ray.experimental import metrics
+from ray.util import metrics
 from ray.serve.config import BackendConfig
 from ray.serve.router import Query
 from ray.serve.constants import DEFAULT_LATENCY_BUCKET_MS
@@ -159,43 +159,72 @@ class RayServeWorker:
         self.num_ongoing_requests = 0
 
         self.request_counter = metrics.Count(
-            "backend_request_counter", ("Number of queries that have been "
-                                        "processed in this replica"),
-            "requests", ["backend"])
-        self.error_counter = metrics.Count("backend_error_counter",
-                                           ("Number of exceptions that have "
-                                            "occurred in the backend"),
-                                           "errors", ["backend"])
+            "backend_request_counter",
+            description=("Number of queries that have been "
+                         "processed in this replica"),
+            tag_keys=("backend", ))
+        self.request_counter.set_default_tags({"backend": self.backend_tag})
+
+        self.error_counter = metrics.Count(
+            "backend_error_counter",
+            description=("Number of exceptions that have "
+                         "occurred in the backend"),
+            tag_keys=("backend", ))
+        self.error_counter.set_default_tags({"backend": self.backend_tag})
+
         self.restart_counter = metrics.Count(
             "backend_worker_starts",
-            ("The number of time this replica workers "
-             "has been restarted due to failure."), "restarts",
-            ["backend", "replica_tag"])
-
-        self.queuing_latency_tracker = metrics.Histogram(
-            "backend_queuing_latency_ms",
-            ("The latency for queries waiting in the replica's queue "
-             "waiting to be processed or batched."), "ms",
-            DEFAULT_LATENCY_BUCKET_MS, ["backend", "replica_tag"])
-        self.processing_latency_tracker = metrics.Histogram(
-            "backend_processing_latency_ms",
-            "The latency for queries to be processed", "ms",
-            DEFAULT_LATENCY_BUCKET_MS,
-            ["backend", "replica_tag", "batch_size"])
-        self.num_queued_items = metrics.Gauge(
-            "replica_queued_queries",
-            "Current number of queries queued in the the backend replicas",
-            "requests", ["backend", "replica_tag"])
-        self.num_processing_items = metrics.Gauge(
-            "replica_processing_queries",
-            "Current number of queries being processed", "requests",
-            ["backend", "replica_tag"])
-
-        self.restart_counter.record(1, {
+            description=("The number of time this replica workers "
+                         "has been restarted due to failure."),
+            tag_keys=("backend", "replica_tag"))
+        self.restart_counter.set_default_tags({
             "backend": self.backend_tag,
             "replica_tag": self.replica_tag
         })
 
+        self.queuing_latency_tracker = metrics.Histogram(
+            "backend_queuing_latency_ms",
+            description=(
+                "The latency for queries waiting in the replica's queue "
+                "waiting to be processed or batched."),
+            boundaries=DEFAULT_LATENCY_BUCKET_MS,
+            tag_keys=("backend", "replica_tag"))
+        self.queuing_latency_tracker.set_default_tags({
+            "backend": self.backend_tag,
+            "replica_tag": self.replica_tag
+        })
+
+        self.processing_latency_tracker = metrics.Histogram(
+            "backend_processing_latency_ms",
+            description="The latency for queries to be processed",
+            boundaries=DEFAULT_LATENCY_BUCKET_MS,
+            tag_keys=("backend", "replica_tag", "batch_size"))
+        self.processing_latency_tracker.set_default_tags({
+            "backend": self.backend_tag,
+            "replica_tag": self.replica_tag
+        })
+
+        self.num_queued_items = metrics.Gauge(
+            "replica_queued_queries",
+            description=("Current number of queries queued in the "
+                         "the backend replicas"),
+            tag_keys=("backend", "replica_tag"))
+        self.num_queued_items.set_default_tags({
+            "backend": self.backend_tag,
+            "replica_tag": self.replica_tag
+        })
+
+        self.num_processing_items = metrics.Gauge(
+            "replica_processing_queries",
+            description="Current number of queries being processed",
+            tag_keys=("backend", "replica_tag"))
+        self.num_processing_items.set_default_tags({
+            "backend": self.backend_tag,
+            "replica_tag": self.replica_tag
+        })
+
+        self.restart_counter.record(1)
+
         asyncio.get_event_loop().create_task(self.main_loop())
 
     def get_runner_method(self, request_item: Query) -> Callable:
@@ -216,17 +245,13 @@ class RayServeWorker:
         start = time.time()
         try:
             result = await method_to_call(arg)
-            self.request_counter.record(1, {"backend": self.backend_tag})
+            self.request_counter.record(1)
         except Exception as e:
             result = wrap_to_ray_error(e)
-            self.error_counter.record(1, {"backend": self.backend_tag})
+            self.error_counter.record(1)
 
         self.processing_latency_tracker.record(
-            (time.time() - start) * 1000, {
-                "backend": self.backend_tag,
-                "replica": self.replica_tag,
-                "batch_size": "1"
-            })
+            (time.time() - start) * 1000, tags={"batch_size": "1"})
 
         return result
 
@@ -248,8 +273,7 @@ class RayServeWorker:
                     "Please only send the same type of requests in batching "
                     "mode.")
 
-            self.request_counter.record(batch_size,
-                                        {"backend": self.backend_tag})
+            self.request_counter.record(batch_size)
 
             call_method = ensure_async(call_methods.pop())
             result_list = await call_method(args)
@@ -274,15 +298,12 @@ class RayServeWorker:
                 raise RayServeException(error_message)
         except Exception as e:
             wrapped_exception = wrap_to_ray_error(e)
-            self.error_counter.record(1, {"backend": self.backend_tag})
+            self.error_counter.record(1)
             result_list = [wrapped_exception for _ in range(batch_size)]
 
         self.processing_latency_tracker.record(
-            (time.time() - timing_start) * 1000, {
-                "backend": self.backend_tag,
-                "replica_tag": self.replica_tag,
-                "batch_size": str(batch_size)
-            })
+            (time.time() - timing_start) * 1000,
+            tags={"batch_size": str(batch_size)})
 
         return result_list
 
@@ -294,21 +315,12 @@ class RayServeWorker:
             batch = await self.batch_queue.wait_for_batch()
 
             # Record metrics
-            self.num_queued_items.record(self.batch_queue.qsize(), {
-                "backend": self.backend_tag,
-                "replica_tag": self.replica_tag
-            })
-            self.num_processing_items.record(
-                self.num_ongoing_requests - self.batch_queue.qsize(), {
-                    "backend": self.backend_tag,
-                    "replica_tag": self.replica_tag
-                })
+            self.num_queued_items.record(self.batch_queue.qsize())
+            self.num_processing_items.record(self.num_ongoing_requests -
+                                             self.batch_queue.qsize())
             for query in batch:
                 queuing_time = (time.time() - query.tick_enter_replica) * 1000
-                self.queuing_latency_tracker.record(queuing_time, {
-                    "backend": self.backend_tag,
-                    "replica_tag": self.replica_tag
-                })
+                self.queuing_latency_tracker.record(queuing_time)
 
             all_evaluated_futures = []
 
diff --git a/python/ray/serve/http_proxy.py b/python/ray/serve/http_proxy.py
index 2d0e2265f..59fb47f38 100644
--- a/python/ray/serve/http_proxy.py
+++ b/python/ray/serve/http_proxy.py
@@ -7,7 +7,7 @@ import uvicorn
 import ray
 from ray.exceptions import RayTaskError
 from ray.serve.context import TaskContext
-from ray.experimental import metrics
+from ray.util import metrics
 from ray.serve.http_util import Response
 from ray.serve.router import Router, RequestMetadata
 
@@ -32,8 +32,9 @@ class HTTPProxy:
         self.route_table = await controller.get_router_config.remote()
 
         self.request_counter = metrics.Count(
-            "num_http_requests", "The number of HTTP requests processed",
-            "requests", ["route"])
+            "num_http_requests",
+            description="The number of HTTP requests processed",
+            tag_keys=("route", ))
 
         self.router = Router()
         await self.router.setup(name, controller_name)
@@ -80,7 +81,7 @@ class HTTPProxy:
         assert scope["type"] == "http"
         current_path = scope["path"]
 
-        self.request_counter.record(1, {"route": current_path})
+        self.request_counter.record(1, tags={"route": current_path})
 
         if current_path.startswith("/-/"):
             await self._handle_system_request(scope, receive, send)
diff --git a/python/ray/serve/router.py b/python/ray/serve/router.py
index aac4b8eac..4ff393044 100644
--- a/python/ray/serve/router.py
+++ b/python/ray/serve/router.py
@@ -9,7 +9,7 @@ from dataclasses import dataclass, field
 from ray.exceptions import RayTaskError
 
 import ray
-from ray.experimental import metrics
+from ray.util import metrics
 from ray.serve.context import TaskContext
 from ray.serve.endpoint_policy import RandomEndpointPolicy
 from ray.serve.utils import logger, chain_future
@@ -139,21 +139,25 @@ class Router:
         # -- Metrics Registration -- #
         self.num_router_requests = metrics.Count(
             "num_router_requests",
-            "Number of requests processed by the router.", "requests",
-            ["endpoint"])
+            description="Number of requests processed by the router.",
+            tag_keys=("endpoint", ))
         self.num_error_endpoint_requests = metrics.Count(
             "num_error_endpoint_requests",
-            ("Number of requests that errored when getting results "
-             "for the endpoint."), "requests", ["endpoint"])
+            description=(
+                "Number of requests that errored when getting results "
+                "for the endpoint."),
+            tag_keys=("endpoint", ))
         self.num_error_backend_requests = metrics.Count(
             "num_error_backend_requests",
-            ("Number of requests that errored when getting result "
-             "from the backend."), "requests", ["backend"])
+            description=("Number of requests that errored when getting result "
+                         "from the backend."),
+            tag_keys=("backend", ))
 
         self.backend_queue_size = metrics.Gauge(
             "backend_queued_queries",
-            "Current number of queries queued in the router for a backend",
-            "requests", ["backend"])
+            description=("Current number of queries queued "
+                         "in the router for a backend"),
+            tag_keys=("backend", ))
 
         asyncio.get_event_loop().create_task(self.report_queue_lengths())
 
@@ -161,7 +165,7 @@ class Router:
                               **request_kwargs):
         endpoint = request_meta.endpoint
         logger.debug("Received a request for endpoint {}".format(endpoint))
-        self.num_router_requests.record(1, {"endpoint": endpoint})
+        self.num_router_requests.record(1, tags={"endpoint": endpoint})
 
         request_context = request_meta.request_context
         query = Query(
@@ -177,7 +181,8 @@ class Router:
         try:
             result = await query.async_future
         except RayTaskError as e:
-            self.num_error_endpoint_requests.record(1, {"endpoint": endpoint})
+            self.num_error_endpoint_requests.record(
+                1, tags={"endpoint": endpoint})
             result = e
         return result
 
@@ -301,7 +306,8 @@ class Router:
             else:
                 result = await object_ref
         except RayTaskError as error:
-            self.num_error_backend_requests.record(1, {"backend": backend})
+            self.num_error_backend_requests.record(
+                1, tags={"backend": backend})
             result = error
         self.queries_counter[backend][backend_replica_tag] -= 1
         await self.mark_worker_idle(backend, backend_replica_tag)
@@ -358,6 +364,7 @@ class Router:
                 self.name, queue_lengths)
 
             for backend, length in queue_lengths.items():
-                self.backend_queue_size.record(length, {"backend": backend})
+                self.backend_queue_size.record(
+                    length, tags={"backend": backend})
 
             await asyncio.sleep(REPORT_QUEUE_LENGTH_PERIOD_S)
diff --git a/python/ray/tests/test_metrics_agent.py b/python/ray/tests/test_metrics_agent.py
index 1c5627199..2c36a5f7d 100644
--- a/python/ray/tests/test_metrics_agent.py
+++ b/python/ray/tests/test_metrics_agent.py
@@ -1,5 +1,6 @@
 import json
 from pprint import pformat
+from unittest.mock import MagicMock
 
 import requests
 import pytest
@@ -7,7 +8,7 @@ from prometheus_client.parser import text_string_to_metric_families
 
 import ray
 from ray.metrics_agent import PrometheusServiceDiscoveryWriter
-from ray.experimental.metrics import Count, Histogram
+from ray.util.metrics import Count, Histogram, Gauge
 from ray.test_utils import wait_for_condition, SignalActor
 
 
@@ -59,16 +60,16 @@ def _setup_cluster_for_test(ray_start_cluster):
     # Generate some metrics from actor & tasks.
     @ray.remote
     def f():
-        counter = Count(f"test_counter", "desc", "unit", [])
-        counter.record(1, {})
+        counter = Count("test_counter", description="desc")
+        counter.record(1)
         ray.get(worker_should_exit.wait.remote())
 
     @ray.remote
     class A:
         async def ping(self):
-            histogram = Histogram("test_histogram", "desc", "unit", [0.1, 1.6],
-                                  [])
-            histogram.record(1.5, {})
+            histogram = Histogram(
+                "test_histogram", description="desc", boundaries=[0.1, 1.6])
+            histogram.record(1.5)
             ray.get(worker_should_exit.wait.remote())
 
     a = A.remote()
@@ -181,6 +182,98 @@ def test_metrics_export_end_to_end(_setup_cluster_for_test):
         test_cases()  # Should fail assert
 
 
+@pytest.fixture
+def metric_mock():
+    mock = MagicMock()
+    mock.record.return_value = "haha"
+    yield mock
+
+
+"""
+Unit test custom metrics.
+"""
+
+
+def test_basic_custom_metrics(metric_mock):
+    # Make sure each of metric works as expected.
+    # -- Count --
+    count = Count("count", tag_keys=("a", ))
+    count._metric = metric_mock
+    count.record(1)
+    metric_mock.record.assert_called_with(1, tags={})
+
+    # -- Gauge --
+    gauge = Gauge("gauge", description="gauge")
+    gauge._metric = metric_mock
+    gauge.record(4)
+    metric_mock.record.assert_called_with(4, tags={})
+
+    # -- Histogram
+    histogram = Histogram(
+        "hist", description="hist", boundaries=[1.0, 3.0], tag_keys=("a", "b"))
+    histogram._metric = metric_mock
+    histogram.record(4)
+    metric_mock.record.assert_called_with(4, tags={})
+    tags = {"a": "3"}
+    histogram.record(10, tags=tags)
+    metric_mock.record.assert_called_with(10, tags=tags)
+    tags = {"a": "10", "b": "b"}
+    histogram.record(8, tags=tags)
+    metric_mock.record.assert_called_with(8, tags=tags)
+
+
+def test_custom_metrics_info(metric_mock):
+    # Make sure .info public method works.
+    histogram = Histogram(
+        "hist", description="hist", boundaries=[1.0, 2.0], tag_keys=("a", "b"))
+    assert histogram.info["name"] == "hist"
+    assert histogram.info["description"] == "hist"
+    assert histogram.info["boundaries"] == [1.0, 2.0]
+    assert histogram.info["tag_keys"] == ("a", "b")
+    assert histogram.info["default_tags"] == {}
+    histogram.set_default_tags({"a": "a"})
+    assert histogram.info["default_tags"] == {"a": "a"}
+
+
+def test_custom_metrics_default_tags(metric_mock):
+    histogram = Histogram(
+        "hist", description="hist", boundaries=[1.0, 2.0],
+        tag_keys=("a", "b")).set_default_tags({
+            "b": "b"
+        })
+    histogram._metric = metric_mock
+
+    # Check default tags.
+    histogram.record(4)
+    metric_mock.record.assert_called_with(4, tags={"b": "b"})
+
+    # Check specifying non-default tags.
+    histogram.record(10, tags={"a": "a"})
+    metric_mock.record.assert_called_with(10, tags={"a": "a", "b": "b"})
+
+    # Check overriding default tags.
+    tags = {"a": "10", "b": "c"}
+    histogram.record(8, tags=tags)
+    metric_mock.record.assert_called_with(8, tags=tags)
+
+
+def test_custom_metrics_edge_cases(metric_mock):
+    # None or empty boundaries are not allowed.
+    with pytest.raises(ValueError):
+        Histogram("hist")
+
+    with pytest.raises(ValueError):
+        Histogram("hist", boundaries=[])
+
+    # Empty name is not allowed.
+    with pytest.raises(ValueError):
+        Count("")
+
+    # The tag keys must be a tuple type.
+    with pytest.raises(ValueError):
+        Count("name", tag_keys=("a"))
+
+
 if __name__ == "__main__":
     import sys
     sys.exit(pytest.main(["-v", __file__]))
diff --git a/python/ray/util/metrics.py b/python/ray/util/metrics.py
new file mode 100644
index 000000000..e7a07b950
--- /dev/null
+++ b/python/ray/util/metrics.py
@@ -0,0 +1,183 @@
+import logging
+
+from typing import Dict, Any, List, Optional, Tuple
+
+from ray._raylet import (
+    Count as CythonCount,
+    Histogram as CythonHistogram,
+    Gauge as CythonGauge,
+)  # noqa: E402
+
+logger = logging.getLogger(__name__)
+
+
+class Metric:
+    """The parent class of custom metrics.
+
+    Ray's custom metrics APIs are rooted from this class and share
+    the same public methods.
+    """
+
+    def __init__(self,
+                 name: str,
+                 description: str = "",
+                 tag_keys: Optional[Tuple[str]] = None):
+        if len(name) == 0:
+            raise ValueError("Empty name is not allowed. "
+                             "Please provide a metric name.")
+        self._name = name
+        self._description = description
+        # We don't specify unit because it won't be
+        # exported to Prometheus anyway.
+        self._unit = ""
+        # The default tags key-value pair.
+        self._default_tags = {}
+        # Keys of tags.
+        self._tag_keys = tag_keys or tuple()
+        # The Cython metric class. This should be set in the child class.
+        self._metric = None
+
+        if type(self._tag_keys) != tuple:
+            raise ValueError(
+                "tag_keys should be a tuple type, "
+                f"but {type(self._tag_keys)} type was specified instead.")
+
+    def set_default_tags(self, default_tags: Dict[str, str]):
+        """Set default tags of metrics.
+
+        Example:
+            >>> # Note that set_default_tags returns the instance itself.
+            >>> counter = Counter("name")
+            >>> counter2 = counter.set_default_tags({"a": "b"})
+            >>> assert counter is counter2
+            >>> # this means you can instantiate it in this way.
+            >>> counter = Counter("name").set_default_tags({"a": "b"})
+
+        Args:
+            default_tags(dict): Default tags that are
+                used for every record method.
+
+        Returns:
+            Metric: it returns the instance itself.
+        """
+        self._default_tags = default_tags
+        return self
+
+    def record(self, value: float, tags: dict = None) -> None:
+        """Record the metric point of the metric.
+
+        Args:
+            value(float): The value to be recorded as a metric point.
+        """
+        assert self._metric is not None
+        default_tag_copy = self._default_tags.copy()
+        default_tag_copy.update(tags or {})
+        self._metric.record(value, tags=default_tag_copy)
+
+    @property
+    def info(self) -> Dict[str, Any]:
+        """Return the information of this metric.
+
+        Example:
+            >>> counter = Counter("name", description="desc")
+                print(counter.info)
+                \"""
+                {
+                    "name": "name",
+                    "description": "desc"
+                    "tag_keys": ("ray.key")
+                    "default_tags": {"ray.key": "abc"}
+                }
+                \"""
+        """
+        return {
+            "name": self._name,
+            "description": self._description,
+            "tag_keys": self._tag_keys,
+            "default_tags": self._default_tags
+        }
+
+
+class Count(Metric):
+    """The count of the number of metric points.
+
+    This is corresponding to Prometheus' Count metric.
+
+    Args:
+        name(str): Name of the metric.
+        description(str): Description of the metric.
+        tag_keys(tuple): Tag keys of the metric.
+    """
+
+    def __init__(self,
+                 name: str,
+                 description: str = "",
+                 tag_keys: Optional[Tuple[str]] = None):
+        super().__init__(name, description, tag_keys)
+        self._metric = CythonCount(self._name, self._description, self._unit,
+                                   self._tag_keys)
+
+
+class Histogram(Metric):
+    """Histogram distribution of metric points.
+
+    This is corresponding to Prometheus' Histogram metric.
+    Recording metrics with histogram will enable you to import
+    min, mean, max, 25, 50, 95, 99 percentile latency.
+
+    Args:
+        name(str): Name of the metric.
+        description(str): Description of the metric.
+        boundaries(list): Boundaries of histogram buckets.
+        tag_keys(tuple): Tag keys of the metric.
+    """
+
+    def __init__(self,
+                 name: str,
+                 description: str = "",
+                 boundaries: List[float] = None,
+                 tag_keys: Optional[Tuple[str]] = None):
+        super().__init__(name, description, tag_keys)
+        if boundaries is None or len(boundaries) == 0:
+            raise ValueError(
+                "boundaries argument should be provided when using the "
+                "Histogram class. EX) Histgoram(boundaries=[1.0, 2.0])")
+        self.boundaries = boundaries
+        self._metric = CythonHistogram(self._name, self._description,
+                                       self._unit, self.boundaries,
+                                       self._tag_keys)
+
+    @property
+    def info(self):
+        """Return information about histogram metric."""
+        info = super().info
+        info.update({"boundaries": self.boundaries})
+        return info
+
+
+class Gauge(Metric):
+    """Gauge Keeps the last recorded value, drops everything before.
+
+    This is corresponding to Prometheus' Gauge metric.
+
+    Args:
+        name(str): Name of the metric.
+        description(str): Description of the metric.
+        tag_keys(tuple): Tag keys of the metric.
+        tags(dict): Dictionary of default tag values.
+    """
+
+    def __init__(self,
+                 name: str,
+                 description: str = "",
+                 tag_keys: Optional[Tuple[str]] = None):
+        super().__init__(name, description, tag_keys)
+        self._metric = CythonGauge(self._name, self._description, self._unit,
+                                   self._tag_keys)
+
+
+__all__ = [
+    "Count",
+    "Histogram",
+    "Gauge",
+]