10 Amazing Hard Rock Songs Featuring Killer Guest Stars

In the era of grunge rock sweeping the nation in the early '90s, no one had heard anything like what Rage Against the Machine was doing. Instead of the typical '70s rock riffs that everyone was getting from Pearl Jam, here were four guys playing metal riffs that hit like sledgehammers all while Zack da le Rocha spit fire behind the mic. So...how does a band like that sound when you put an actual singer behind them?

While Zack was the perfect frontman for Rage, none of his verses were ever steeped in melody, which makes the verse from Tool's Maynard James Keenan in Know Your Enemy almost come out of nowhere. From the moment the song starts, it feels like a typical Rage stomper track, but the Maynard verses puts a whole different spin on what you were originally thinking, sounding more tortured than political.

Hell, combined with the drop D riff from Tom Morello and Maynard's vocals, this has all the trappings of a good Tool track, which makes sense considering that guitarist Adam Jones was actually in a band with Morello before either of them got off the ground in the first place. Still, this does provide a nice example of what a band like Rage could have sounded like if things ended up working out just a little bit differently.