Metrics are just ways of measuring things. They are consistent systems of measurement.
"Consistent with what?" is the best question to ask about them. This often reveals the mind-set and point of view from which metrics were defined, and numbers compiled. Also, quite importantly, whose judgement is to be trusted when setting specific tests for inclusion or exclusion in statistics. The book How to lie with statistics outlined some of the issues.
In the Vietnam War, reliance on bad metrics such as the infamous body count, tended to make bad decisions worse. Management theories today often warn about the dangers of bad metrics, using this war as a potent example.
In a bureaucracy, metrics provide a handy means of responsibility evasion. If someone actus foolishly but the metrics say something has been achieved, they can excuse themselves simply by referring to the metric. An infinite amount of incompetence can be excused in this simple way.