Amount of 4xx, 500, and 2xx of an http application can tell a lot about application anomalies. Other protocols also have their error responses.

I also keep a close eye in the throughput VS response time ratio, specially the 95th percentile of the resp time.

It’s also great to have this same ratio measurement for the DBs you might use.

Those are my go to daily metrics, the rest can be zoomed in their own dashboards after I first check this.