EDIT: Tracing deals with annotating methods, and how long they take. E.g. function a took 3 seconds, and make 2 DB calls that took 1.4 seconds. Metrics deal with how many times you made calls, how long they took, etc. So two importantly related parts of application monitoring.

Metrics is different to Tracing in this case. From the surface (or from someone who doesn't closely follow), OpenCensus contains metrics and tracing (and maybe more).

OpenMetrics appears to be the standardising the metrics part, hence the sentence that OpenMetrics is being integrated with OpenCensus.

Now, you might ask, because I've also asked: what are the pros/cons of Census over Tracing for tracing purposes?

It does look like both standards compete and perhaps diverge. I once sensed a bit of bashing of the latter in the OpenCensus Gitter channel; which convinced me to just stay with OpenTracing as they already had more integrations at the time.

At least Metrics is being promoted by the same interests as those working on Census, so we won't see another set of standards targeting the same applications (LightStep, StackDriver, etc).

In short, why can't OC and OT combine their efforts?