Well, if you want a really HEAVY metal version of traditional folk, check out Liam aka Mephisto Grande from Oxford. His mom played old-time fiddle, and he grew up going to lots of folk festivals. Altho mostly he does his very extreme original stuff, he will occasionally throw in "Will the Circle Be Unbroken" or traditional gospel tunes, etc. in a VERY non-traditional way.   

Warning, this AIN'T your mama's folk!

if you do run into him, tell him I said "hi".