These threads asking for recommendations for metal-friendly cans pop up pretty regularly, and it seems like there is a lot more good information in this one than most of the others I've seen. Interesting reading.
I also listen to metal significantly more than anything else (although I tend to listen to more extreme stuff, Dillinger Escape Plan, Psyopus, Meshuggah, etc), and to my ears the orthos do really well with presenting the music in a clear but listenable way. Within (or at least close to) your budget, I would point you towards two cans in particular: the Mad Dogs (which someone else already recommended), and the HiFiMan HE-400. I got to listen to both of these for the first time a couple of weeks ago, and I was highly impressed. The Mad Dogs are closed and seem to be a bit more forgiving (although a bit dark-sounding) if that's your preference, while the HE-400 is open and seems more treble-tipped than the Mad Dogs. Either one of these would require an amp to really get good sound, but you could probably pick up an O2 amp used at a decent price, which I would think would drive either pretty well.
Regarding recording quality: people tend to muddle up the logic on whether good or bad headphones are better or worse for poorly recorded music IMO. Yes, the better you gear is, the more able you are to hear the flaws in it. But you're also able to hear a lot of other positive stuff you might otherwise miss: the sound of a really good guitar tone and texture, the pick flicking across the strings, and a better idea of what some of the more technical wizards out there are actually doing with their instruments. Ultimately, poor recording quality just sucks no matter what you listen to it on, and having crappier headphones doesn't change the fact that you're listening to poorly recorded (or mixed, or mastered, whatever) music. As an example, there were two excellent metal albums that came out recently: Dillinger Escape Plan's One of Us Is The Killer and Leprous' Coal. The DEP album is noticeably compressed, and while it gets annoying in several specific passages on the album, it really starts to add up as you listen to the entire album and makes you want to turn down the sound because your ears get fatigued. In contrast, the new Leprous album is very well done and sounds great the entire way through, and you never really find yourself wanting to keep creeping the volume lower and lower-- you just want to listen to the subtle complexity that lies behind their more straightforward approach on this album. As an aside, this is one of the major reasons I collect vinyl albums for metal bands I like-- when I finally get around to picking up an ADC that I like, I can rip the vinyl albums into digital and sidestep the compression effects of the loudness wars and thus enjoy the music as it was actually meant to be heard, without idiotically restricting the dynamic range of the music as some albums do. Sigh. [/rant].
And as a final aside on recording quality, nothing is ever going to make some of the early black metal stuff sound good. The music itself is pretty great on a few of them, and the technical chops possessed (ha!) by some of those guys is really impressive, but they were intentionally recorded to sound bad-- it was part of the whole 'no scene, no mosh, no core' movement at the time. Silly, I know, but them's the breaks.
As far as what types of sound signatures work well with metal, my experience is that the more clear, transparent, and detailed the sound, the better for all types of music, metal included. I absolutely love my T5p with metal, for example, even though it's a bit lacking in bass quantity, because it is so unbelievably clear and detailed. I'm actually a bit more likely to reach for my T5p for metal than my LCD-2 a lot of the time because of that addictive clarity. (Although the LCD-2 is still awesome, and I still love it with metal).
Ultimately, if you can get to a meet and get a chance to hear some of this stuff, it's going to be your best bet. You won't know what you like until you actually get a chance to listen to a few things, and your preferences might surprise you-- I found that while I thought I would prefer a lush, PRAT-ty approach, I actually just enjoy the most neutral sound I can get. Whoda thunk?
Keep us posted on your progress, and good luck man ;)