mettle vs bravery

mettle and bravery both are nouns.

Word	Noun	Adjective	Verb	Adverb
mettle	Yes	No	No	No
bravery	Yes	No	No	No

As nouns, bravery is a hypernym of mettle; that is, bravery is a word with a broader meaning than mettle:

mettle: the courage to carry on
bravery: a quality of spirit that enables you to face danger or pain without showing fear

Other hypernyms of mettle include braveness, courage, courageousness.

mettle (noun)	bravery (noun)
the courage to carry on	a quality of spirit that enables you to face danger or pain without showing fear
	feeling no fear