A metric is a measure, possibly a performance goal in this instance. Calls with result vs calls per hour with no result for telemarketer for instance. Minimum sales volume for new salesperson per quarter. Units produced per hour for factory team, and the like.
Cannot be done unless each person is pulling his weight, linked to pay for performance. Could be more specific if you had specified the job.
It might mean too that they want a person who is familiar with the Metric System, can use metric system units of measure, knows one inch = 2.54 cm, one km = .62 mile and the like, is not thrown off by using nanometers (nm) for spectroscope, or metric wrenches or whatever. But I doubt that applies to the question.
More likely they are referring to meeting performance goals. Farm work would be hay bales per hour, weight of corn harvested per day and the like.
Usually there is some minimum which they know indicates goofing off if a person does not meet it. The diligent people all exceed the minimum, some by a lot.
I have done LOTS of different work. Found out I am slower than most, BUT I ALWAYS got more work done. That is because I never goof off and focus on my work -- which I do with QUALITY. So even though I am slower than others, I get more work done and there is high quality, none of it is rejected or needing to be redone.
Some people gossip and waste time, talk on the phone (not work related) and such, especially when working where there is a smaller group or a small office with no monitoring. Like the fat gal you see talking on the phone for half hour on personal while you are waiting at the customer service window in the doctor's office and are very ill. She does not care, is not attentive to quality.
"Achieving metrics" appears to be a policy there. They will weed out those who do not "achieve metrics."
Simple: Pay attention to how those who "achieve" metrics are getting it done. Learn their methods and copy them carefully. Do not worry so much about speed as getting it done RIGHT. Further practice doing it right will enable speed as the proper actions become second nature.
Doing your work carefully not only gets it DONE, but means it is really DONE (with quality and needing no repairs).
If you do sloppy work and watch the clock the work day is long. If you focus on your job and do not loaf or waste time, you hear the end bell, and the day has gone by fast, and your production stats are high, and maybe you get a pay raise. Those who produce more should have higher pay than others.