Many artists never have guests on their albums. ZZ Top, for example, not only don't bring in guest stars, they don't let anyone but them play on their records; when it came time to feature horns on 1979's Deguello, rather than break their own rule by renting a horn section, the bandmembers learned to play trumpet and saxophone. But other bands enjoy the injection of energy that an unfamiliar face or voice can provide. For this week's Spotify playlist, we've come up with 10 examples of Roadrunner bands bringing in a guest vocalist to add a little something special to a track.

Megadeth, "A Tout le Monde" from United Abominations (Buy it) - This ballad has become one of Megadeth's best-known songs, and was a major highlight of their 2012 Gigantour dates, when the guest vocalist, Lacuna Coil's Cristina Scabbia, came onstage to sing it with Dave Mustaine every night.

Cradle of Filth, "Nymphetamine Overdose" from Nymphetamine (Buy it) - This nine-minute epic features the sounds of a roaring crowd punched in via studio magic, as well as a thrilling guest vocal by Liv Kristine of the European folk-metal act Leaves' Eyes (she's also the wife of Atrocity's Alexander Krull, who engineered the record).

36 Crazyfists, "Elysium" from Rest Inside the Flames - This Alaskan metalcore band needed to add some extra punch to a track from their third album, so naturally they brought in Howard Jones, then of Killswitch Engage, to put some vocal muscle on the chorus. It worked.

Cavalera Conspiracy, "Lynch Mob" from Blunt Force Trauma (Buy it) - Cavalera Conspiracy didn't just represent a chance for Soulfly's Max Cavalera to reunite with his brother Igor; it also allowed him to explore his roots in hardcore, no more so than when Agnostic Front's legendary frontman, Roger Miret, contributed his instantly recognizable bark to this track.

Fear Factory, "Cars" from Obsolete - How can you cover an absolute New Wave classic, not to mention Gary Numan's only US hit, without inviting the man himself to sing on it (and appear in the video)? Fear Factory knew this couldn't be a cover without also being a collaboration, and the result was awesome.

Coal Chamber, "Shock the Monkey" from Chamber Music (Buy it) - This song came totally out of left field. Nobody expected Coal Chamber to cover a Peter Gabriel song on their highly regarded second album, and they certainly didn't expect a heavy metal god, Ozzy Osbourne, to sing the chorus. But there he is!

Sepultura, "Lookaway" from Roots (Buy it) - This track is practically a summit conference of instantly recognizable vocalists. Not only do you have Max Cavalera roaring and growling, but you've got Faith No More's Mike Patton and Korn's Jonathan Davis backing him up. You can't get much more crazed than that.

Within Temptation, "What Have You Done" from The Heart of Everything (Buy it) - This power ballad by the Dutch symphonic metallers featured a fairly surprising ringer; Life of Agony frontman Keith Caputo shows up, delivering an intense and even romantic duet with singer Sharon den Adel.

Soulfly, "First Commandment" from Soulfly (Buy it) - The debut album by Max Cavalera's post-Sepultura project was practically an all-star session, with multiple tracks featuring guests. None was as impressive as this one, though, which found the Deftones' Chino Moreno backing Max up.

Theory of a Deadman, "By the Way" from Scars & Souvenirs (Buy it) - This Canadian band brought in a longtime friend of singer Tyler Connolly, Chris Daughtry, to sing on this anthemic rock track. The two men's voices deliver both grit and surprisingly affecting harmony, making the track's success on radio no surprise at all.

Listen to the whole list now on Spotify!