I take it you are referring to a Heavy Metal type dound doing trad/folk stuff.
There is probably ( in my opinion) a few things I'll find interseting but a majority I'll find awful - I'm NOT referrring to electric folk/folk rock as in the groups ChantyWrassler mentioned. (and note I liked what we called Hard Rock in my day - and still do - Led Zepellin (BBC sessions are great), refraining from going on a real nostalgia trip and getting Paranoid by ZBlack Sabbath (saw them at Birmingham Town Hall in 1970) and so forth,
I found the Swedish group Hoven Groven to be really intereting. Made a massive mistake in this other "Celtic-Rock" group which seems to have a following - "Tempest"
A few years ago I found the Levellers to be good - but it is probably more punk-folk!
Anyway, I suppose I'm saying that if I like it it is interesting and "valid", otherwise it can be noise. But then someone's meat is another person's poison - so if you like it, it's valid
Rana