Try out several headphones whenever possible before you buy, especially if you are spending significant money on them.
You can try the ATH-M50x at a Guitar Center (I'm sure there would be other places as well). They would have plenty of other options so try as many as you can while you're there. I was thinking of getting M50s as well, but when I listened to them I was not all that impressed. I'm not a bass head, but if you are, you might like them. Even if you're not, you might like them anyway so don't let me discourage you. Keep in mind that a noisy environment like GC might make you favor noise isolating headphones while you're trying them out, but at home you might prefer something else.
If you can find somewhere that has them, try out some Grados. I went with the SR125i and love them for pretty much everything that i listen to. I have read that Grados can be polarizing when it comes to peoples opinions of them, so you'll probably want to try them first. They aren't circumaural or closed back like the M50s. If that's what you're looking for, I still recommend you try them as they might change your mind. I wasn't sure I'd like then, but after listening to them I was convinced.
A variety of the metal bands I listen to include: In Flames, Dream Theater, Tesseract, Meshuggah, Slayer, Wintersun, etc.
