Well I have the HD598 and I do listen to a lot of metal and have to say they're really good for it. I can't really complain on any part, the bass is powerful and well controlled but not overpresented, so you get weighty kicks while still being able to hear the rest. Mids are probably my favourite on these headphones, both electric and acoustic guitars sound beautiful, also it manages to reproduces all kinds of vocals (clean/harsh female/male) very well. No problem on the high end of the spectrum, cymbals sound very realistic, not the annoying type.
None of the music you mentioned is really the audiophile type, especially not Burzum, but I really love it on the 598 and actually managed to discovery some new details, like there's a quiet drumming in the song Tomhet from the very beginning. Yeah, I mentioned Tomhet for a reason, these kind of ambient stuff goes hand in hand with these cans, since they have huge and totally three dimensional soundstage thus the music surrounds you proving a truly transcendental listen. All kind of ambient is a great match, black ambient like Burzum, Lustre, dark ambient like Lustmord or Kammarheit or the more neo-folkish acoustic/post-rock ones like Ulver, Vali and Kauan. I also like the "standard" black metal on these, I was really amazed when first listened the album Nattens Madrigal, I never though instruments could be separated so well in such a recording. As others said the 598 is very musical and a fun listen so folk is very engaging and uplifting on it. You might not get all the details here, but it will make you happy and I think that's what people expect from folk metal. Doom also sounds as it should heavy and desperate, due to the described bass (and low mids), I really like the kicks in Candlemass and vocals in Acid Witch with with these phones.
As you can see I'm totally positive on the 598, but to be fair here are some cons: Probably not the best price/value ratio, you could get more analytical headphones for this money, and they may crack, though warranty covers that.
(Sorry for my bad wording and grammar mistakes, I'm a bit tired.)