You will find a metrics formatter package for each of the time series database support packages, as well as some more generic formatter packages included in App Metrics such as App.Metrics.Formatters.Ascii & App.Metrics.Formatters.Json.
Formatter packages allow metric snapshots to be serialized, they are designed be used with a reporter allowing us to Push metrics or wired-up with a web application allowing us to Pull metrics or even to simply view over an HTTP endpoint.
You can find more information on formatting metrics in the Getting Started documentation, including how to implement a custom metric formatter if for example you are wanting to add support for a new reporter.