9. Lateralus - Tool
One of the biggest cliches that comes with being into metal is for how Neaderthalic some of it can sound. As much as some people might have some real power behind their sound, it's the main consensus that most people who listen to this music aren't particularly the most evolved humans in the world. Some of that may be true, but you almost need a graduate degree to fully understand what Tool were doing on Lateralus.
Coming out of the '90s (a decade that was too cruel to metal), Tool created some of the most mind melting songs in metal history on this project, toying around with different time signatures while also being out of their mind on psychedelic drugs. Compared to other metal acts singing about war and death, the lyrics from Maynard James Keenan deal with much more philosophical topics, going from songs about separating the spirit from the body on Parabola to viewing the world as a spiral of existence that we continually ride on the title track.
Even if you distance yourself from what the lyrics are getting at, the ground that they're built on has riffs that are tougher than concrete, from the juicy basslines that open Schism to the tricky time signatures that you have to maneuver your way through just to get through half of these songs. It might be a lot to take in all at once, but if you're familiar with the prog scene even remotely, this is going to be Heaven for you.