Metering is measuring light.
Exposure controls the tonality of your photograph that is recorded onto light sensitive material (digital sensor, film, etc.)
Metering is an evaluation.
Exposure is a decision.
Meter for what you find important in your photograph. (Evaluation)
Expose for how bright or dark you want your picture to be. (Decision)
Metering and exposure are important elements of your composition and should be done attentively and thoughtfully
If asked, could you tell someone what you metered off of and why you decided on your exposure settings?
In other words, did you do the evaluating and deciding or did your camera do it for you?
