In obsolete terms the difference between met and ment

is that met is past tense of mete to measure while ment is past tense of meng.

As verbs the difference between met and ment

is that met is past tense of meet while ment is past tense of meng.

As an abbreviation Met

is the London Underground Metropolitan Line

As a noun MET

is metabolic Equivalent of Task, or simply metabolic equivalent, a measure of the intensity of aerobic exercise.