riffs that have been calculated very specifically so they are all in the same key etc.
DEP etc
i think its just technical metal with weird time signatures that change often
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Quote by dk2
Isn't it just technical metal with complex time signatures?

That's what I've heard most people define it as. Math metal contains a lot of different time signatures throughout an entire song, which for a lot of regular guitar players might be hard to do if they're used to sticking to 4/4 or 3/4 for an entire song.

Tool uses some weird time signatures but nothing too extravagant to be considered math metal.

Also math metal has a lot of dissonant notes and sounds that most wouldn't consider to sound "good." They also usually have some technically complex ****.

Listen to Behold the Arctopus for some pretty badass bass and alright guitar math metal.
Quote by Shred Head
This doesn't belong here ... but if you were wondering, read this

this is musician talk

technically it does and if you dont like it
**** off
For some math metal bands check out, The Dillinger Escape Plan, Psyopus(sp?)
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Quote by Skrying
this is musician talk

technically it does and if you dont like it
**** off

If you asked us to discuss the theory behind "Math Metal" it would belong here. However, since the question is so vague and doesn't have to do with theory, it would belong in the Metal forum (although, you also could have just tried looking it up online).

(Slightly outdated) Electronic and classical compositions by m'self: Check 'em out