Howdy … can you elaborate on where you are looking at metrics? I am assuming you are looking at the Google Cloud Console and drilling into project metrics there. The Google Cloud Monitoring dashboards show metrics collected by Google Cloud for customer usage of Google Cloud resources. The list of potential metrics that are captured are listed here. Since gmail is part of the Google Workspace offering, I wasn’t surprised to see no indications of monitoring metrics captured in Google Cloud. I did come across this article on retrieving email metrics. What kind of metrics are you looking to find?
I then thought of doing a search at Workspace web help and found these.