Telemetry = there is explicit code for end users to track how they use a site, can even be used to identify the user if wanted
Metrics = Current status of an application is being captured, there is no chance or only an almost non-existent chance of identifying which user a request belongs to.
For example, Gitea and thus the metrics only know at best that there was a request at this time to this URL, but they don’t know who called it, or what else they have already done