metier vs line of work

metier and line of work both are nouns.

Word	Noun	Adjective	Verb	Adverb
metier	Yes	No	No	No
line of work	Yes	No	No	No

As nouns, line of work is a hypernym of metier; that is, line of work is a word with a broader meaning than metier:

Other hypernyms of metier include business, job, line, occupation.

metier (noun)	line of work (noun)
an occupation for which you are especially well suited	the principal activity in your life that you do to earn money
an asset of special worth or utility