Originally posted by Bezrael
Contrary to popular belief, Meshuggah never uses anything but 4/4 time, ever. They use complex polyrhythms that are played over common time to make it sound like they're playing in weird time signatures.
Theory is just a tool, not an end unto itself. Bands like Dream Theater, Tool, and Opeth implement theory to structure their music and make it more interesting, but it's how it sounds in the end that matters most. Bands like Dillenger Escape Plan and Spiral Architect use it as an end unto itself, basically saying "look what I can do!" That's why their music sucks.
Tool isn't technical in that their music is difficult to play, but it's extremely well composed and innovative, making excellent use of theory. Danny Carey's drums are especially interesting.