folk metal vs folk music

folk metal and folk music both are nouns.

Word	Noun	Adjective	Verb	Adverb
folk metal	Yes	No	No	No
folk music	Yes	No	No	No

As nouns, folk music is a hypernym of folk metal; that is, folk music is a word with a broader meaning than folk metal:

folk metal: a fusion genre of heavy metal music and traditional folk music that developed in Europe during the 1990s.
folk music: the traditional and typically anonymous music that is an expression of the life of people in a community

Other hypernyms of folk metal include ethnic music, folk, heavy metal, heavy metal music.

folk metal (noun)	folk music (noun)
a fusion genre of heavy metal music and traditional folk music that developed in Europe during the 1990s.	the traditional and typically anonymous music that is an expression of the life of people in a community