It really depends on what sort of metrics you are looking to use.
Cloudera Manager does not store host and service information in the Cloudera Manager database. Rather, that information is stored via leveldb on your OS file system. timeseries queries can be run against Cloudera Manager which whill issue the query to Service/host monitor and return results.
For more information on metrics in CM and tsquery language:
Cloudera Manager api also provides REST API and API calls to perform timeseries queries. Search in your browser for "timeseries" here:
An alternative to this is metrics2. Cloudera documenation regarding how to expose metrics2 to a couple common tools here: