Outside of Kraftwerk, sci-fi may have no greater music ally than metal. Everyone from Rod Serling to Isaac Asimov has explored the concept of machine becoming man, but few have done so as effectively as Judas Priest, Meshuggah and White Zombie.
Judas Priest, "Metal Gods"
Set to a chugging riff and the original synchronized headbang, Rob Halford belts a fantastic tale (read the lyrics) of robots reaping their vengeance on mankind. Should the machines ever rage against us, I'd hope we'd get a soundtrack like this to fight them off with. There's also an obvious pun in the title, but the Priest should be commended for understating their status in the music world.
Meshuggah, "Future Breed Machine"
Jens Kidman's accent and death growl make the lyrics (read here) particularly indecipherable, but the music sounds like the A.I. creation it describes--unpredictable, heavy, fast and destructive. Pushing even the most proficient metal into a new arena (figuratively and literally,) "Future Breed Machine" is one of Meshuggah's best songs, and one that still sounds as brutal as any death metal you'll hear.
White Zombie, "More Human than Human"
The sci-fi stylings of Rob Zombie's first band are usually beyond campy, but for their greatest song Rob took inspiration from a line in Blade Runner, which is as unimpeachable as anything that sci-fi's ever offered. What the rest of the words mean is anybody's guess (check 'em out,) but it all sounds pretty beast over that killer slide guitar lick.