K701 is great for metal, try cranking the original Painkiller cd. Get an O2 amp for it though because it needs it. You could try a Yamaha Pro 400. It really does a great job making metal drums sound like real drums instead of the kicks sounding like clicks. Takes the edge off some of that harshly recorded stuff. good head-banging bass that metal needs. Ain't the most comfortable thing to wear. Sennheiser Amperior is pretty good too but it has this insidious type of fatigue that slowly builds instead of hitting you right away like a Grado. 701 is the only open phone I'd really use for metal. A good test is to try and play Testament's Dark Roots. See if the headphone can hide the horrible sound of that album. It's unlistenable on every headphone I've tried it on aside from the 701 and 400.
for metal a headphone needs to be able to do the following:
-give space for everything
-take the edge off all these hot recordings
-provide head-banging bass
-have enough speed so the music has some life
the problem I see with a lot of phones is that they trade bass for clarity and vice versa. The Yamaha is capable of reproducing even subwoofer kinda bass without sacrificing much clarity. The 701 can be cranked really loud because it leaks sound, and thus loses a good amount of the bass. But it doesn't really have a harsh edge either. I haven't found a phone that is comfortable to wear that also makes metal good to listen to on. Domination by Morbid Angel is an album I use to test phones with. It's a bit muddy so it sounds lean and mean when the 701 drops some of the bass. On the 400 the bass drums don't sound like clicks and they vibrate the earcups without mucking up the sound. But it does stay true to the album's muddy production. You can eq the bass down if you don't want the earcups to rumble. And it's not loose, flabby bass. You can distinctly hear the bass guitar well with these as well as individual kicks on the bass drum. Something like Helloween-Keeper part 1 original cd version will sound fuller, but you won't get the subwoofer style bass Domination gives. To bid you farewell from Opeth sounds gorgeous on these because the Yamaha really do string, wood, and brass instruments well. When an acoustic guitar is picked, it really sounds like a string being picked. I thought the 400 did well with Anthems from Emperor but it couldn't really make IX Equilibrium sound awesome. It brought some much needed body and bass to Spider's Lullabye. That album sounds bass anemic on most everything else. If you play the original cd of Somewhere in Time, you can hear the ride cymbal throughout Caught Somewhere In Time. 400 makes that album's production a lot stronger sounding.