MESHUGGAH

When you just want to hear something that is rough, complex, and heavy, I recommend breaking out some Meshuggah. They're classified as math-metal and experimental metal, so if your looking for something normal Meshuggah isn't what you're looking for. The riffs are blistering and use complex timing.
For those who don't like too heavy of music, I recommend their first cd Contradictions Collapse; it sounds like a heavier (but not too heavy) Metallica. My two favorite albums of what I've heard are Catch 33, and I. Both of those cds are actually one song. Catch 33 is one song but is divided into 13 tracks whereas I is a one track album. The track is 21 minutes, but don't be deterred; these albums do not feel like one song. Meshuggah's current album, Obzen is also very good, but is a little less complex then some previous albums. Another favorite album is Chaosphere. This is a great album which incorporates all the great elements of Meshuggah, with complex timing and occasional avant garde jazz elements.

I recommend you start with: Disenchantment, Entrapment, Dehumanization, Rational Gaze, Combustion, New Millennium Cyanide Christ and I

MR. BUNGLE

I found out about this band a while ago but i never truely checked them out. I rediscovered them and I am so glad I did. This band mixes Metal, Jazz, Funk, Electronica, circus music, ska etc... As it sounds, this band is awesome to listen to and is a big mix of a lot of genres together

They have three albums, Mr. Bungle, Disco Volante, and California.

• Mr. Bungle is the best cd to listen to first to see if you like Mr. Bungle, it is my current favorite.

• Disco Volante is an incredibly weird album considered to be avant-garde metal. Hardcore Mr. Bungle fans will love this album but it certainly needs some getting used to

• California is another great album that has a cool swing feel to it
  

I recomend you start with: Carousel, Stubb (a Dub), My Ass is on Fire, Desert Search for Techno Allah and Goodbye Sober day