folk metal vs ethnic music

folk metal and ethnic music both are nouns.

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

As nouns, ethnic music is a hypernym of folk metal; that is, ethnic 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.
ethnic 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 folk, folk music, heavy metal, heavy metal music.

folk metal (noun)	ethnic 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