I'll reinforce the tuning thing. If you tune a decent drum really well and use appropriate heads (pinstripes are an easy way to get a deep thuddy sound for toms, whereas single ply clear heads may ring too much for most metal applications), you wont need much muffling, if any. The kick is a different story of course. You may want to kill a bit of sustain on some of the toms or snare, but dont go overboard, because if the drums sound dead, they'll get buried by guitars, so a bit of ring is favorable, as long as its controlled. Use overheads as you would any other style of music, but try to close mic all the drums if you can. Part of the Metal drum sound is having everything right in your face.
For a real metal kick sound, use triggers if possible. I'm probably going to get a lot of shit for saying that, but its the truth. There are ways to get a good kick sound from your drum, but you're basically going to be trying to make it sound like a trigger anyway (very little dynamics, every hit as punchy as possible), so why beat around the bush. Granted, if you want a more natural sound, take the time to mic the kick, I'm just saying if you're wanting anything resembling say, Nile, Fear Factory, Killswitch Engage, etc, triggers are the way to go. If you have a DAW you can mic the kick with a radioshack mic and trigger it in your software if you want. Whatever. I dunno. Man I'm probably going to get a lot of shit for the trigger thing.