Everything starts at the source.
SO......
Good guitar, made out of a solid piece of wood. New strings and Good pickups, EM81/85 guitars record great for metal because for some reason they are tighter. When I say tighter I mean the chugs seem to cut off quicker making for clearer notes. I also have liked burstbuckers, dirty fingers and barenuckle pickups as well.
Good amp, 5150, dual rec, slo, ubershall. Just as important is a good cab with good speakers. I like solid cabs with vintage 30s with all the amps I listed. They are mid heavy and seem to kick in the right freq range. They also don't seem to have the weird upper mid fuzz that G12 75s have. Then good settings. Then good mic placement. There are several mics that work: the 57, the 421, the 121, the woodpecker, the 441, the i5, and I'm sure there are more. Don't scoop mids, unless your using a 5150. That amp just seems to be honky in general :lol:. I tend to run my mids on that amp at no more than 4.
Layering: It's good to layer. I have done 4 tracks (4 separate performances, do not copy), but at least 2 is good.
Bass: Again, a good bass made out of wood (I hate composite basses). My favorite is an American J bass with new strings. Good DI or bass amp, I prefer 10" drivers when using a bass as they seem to record better for this genre. I use a D112, but the 57 is good as well. Never tried anything else. I end up using DIs more than amps because it's rare that a bass player in a metal band has something worth a crap. :lol: That said I did have a mesa Titan V12 come in recently and that thing rocked with a D112 in front. I don't mind the sansamp, not my favorite though. I have a BBE bass pre that rocks when you disable the onboard sonic maximizer and compressor.
Drums: The one genre where fake drums run rampant. :lol: Either they are being done from scratch with programs like Steven Slate or Superior 2, or they are being blended with the acoustic set. Seeing triggers on a drumset instead of mics is not uncommon. If you go with the real deal, like any other genre it is IMPERATIVE to have new heads that are tuned correctly. This genre also calls for close micing all the drums and having an OH spaced pair. The 3-4 mic setup sucks for modern metal. Surprisingly, a large kick is not the greatest. I actually personally like 20" kicks more than 22" kicks for this genre.
Vocals: Meh, not anything really that special here. Either the singer sucks or the singer rules. Capturing him with a mic isn't that difficult you just have to select the right one. Sometimes that's a LDC sometimes it's a dynamic. Depends on the voice.