Ronnie James Dio ruined Black Sabbath.
Kill yourself.
Controversial opinion:
I am currently in a disagreement with a friend regarding the worth of folk metal (bands like Korpiklaani, Eluveitie, Ensiferum, Finntroll, etc, his favorite shit on the planet), vs folk-
influenced metal (bands like Drudkh, Agalloch, Ulver, Primordial, etc).
Folk metal generally tries to push the "folk" aspect right in your face, with multiple layers of various "folk" instruments like flute, violin, accordion. From what I can gather, my friend is of the opinion that the more layered the sound, the better.
Folk-influenced metal, rather than relying on plethoras of instruments, opts for atmosphere alone; a stripped-down, more subtle, old Scandinavian/Pagan sound. I think an acoustic guitar is really the only additional instrument a band needs to make true, quality folk-inspired metal.
Now for the opinion: I simply think that folk metal music with various instruments crammed in, stuff of the former category, sounds fucking silly, juvenile, and obnoxious, and is only really "folk" in surface value only. I feel that folk-influenced bands of the latter category, play folky music that is much more mature, well-written, tasteful, and has much more substance.