He also saves an entire planet with music in the 3-D film Captain EO.
He also has magical, musical powers in the totally insane short film Ghosts.
The "Fight For Your Right" sequence that opened the original version of the Black or White short film.
In Tenacious D in The Pick of Destiny, a shard of the devil's tooth is used to create the best rock music of the ages. JB dreams of using the pick to perform supernatural musical feats, such as literally blowing his audience's minds and bringing women to orgasm. The band later gets into a rock-off with the devil over the fate of their souls. The devil's song is a "masterpiece" and their song is "fucking lame," so the devil tries to take Kage to hell. He fires his evil energy at them, prompting JB to leap in front of the blast. His guitar, given to him by Kyle, reflects it back at the devil. This knocks his horn off, which allows Jables to send him back to hell.
In School of Rock, Jack Black's character teaches his class the power of self-confidence through rock 'n roll.
At the end of the Ralph Maccio film Crossroads, it came down to a blues guitar duel with the devil's servant, Jack Butler, played by and based onSteve Vai. In an oddly meta twist, Vai also who composed the piece that Ralph Macchio uses to defeat Jack, and dubbed the guitar part over Ralph's miming. So, essentially, Steve Vai defeated Steve Vai in a guitar duel.
Actually it was Ry Cooder who both played the slide guitar and acts as a hand double for Ralph.
While they did not played music, the Kissmyanthia army from Role Models deserves a special mention for they are based on the legendary rock band KISS.
In Young Einstein, an atomic beer keg is going to go off because it has reached supercritical mass! What can our hero do? Why, plug an experimental electric guitar into it and rock out! What else? A physicist listening on the radio notes with awe: "Electrified music played in 4/4 time!?! That would drain the power out of anything!"
Add heaps and heaps of The Power of Love to this, top it off with a Bittersweet Ending, and you've got yourself Once. It's honestly a very good movie, mostly because they play this trope completely straight.
Casablanca. Victor Laszlo overhears Those Wacky Nazis singing a patriotic (and anti-French) German song around the piano, goes over to the band, and gets them to play La Marseillaise, with Rick's approval. The entire bar joins in, drowning out the Germans and emphasizing the passionate political undertones of the refugees and is the beginning of Rick's redemption.
In Blues Brothers 2000, when the Blues Brothers do "Ghost Riders in the Sky," they summon bad weather, the devil's herd, and the ghost riders; lightning even strikes down a sniper. And the "In the Blood/John the Revelator" sequence was certainly doing something.
In Evolution, singing "You Are So Beautiful To Me" brings the flying monster to the main characters in the mall, only for the poor thing to be gunned down.
Shrek the Third, when Snow White unleashes the power of Led Zeppelin's "Immigrant Song", causing the forest animals to attack the Huorns guarding the city gates.
Apocalypse Now creepily deconstructs this, when "Ride of the Valkyries" is played as the American helicopters shoot up a village. Because of the unpleasant connotations "Valkyries" has picked up, and the decidedly unheroic nature of the scene, it's not exactly rock-out material.
J Men Forever, a 1979 Gag Dub of Republic Film Serial clips, has the villainous Lightning Bug scheming to conquer the Earth with Sex, Drugs and Rock & Roll. His rock broadcasts from the Moon are powerful enough to cause cars to crash, cities to collapse, and record moguls to commit suicide. The J-Men counter this by broadcasting schmaltzy music, and the Lightning Bug eventually blows up the Moon when he cranks up his stereo too loud.
In the 1985 comedy Water the island of Cascara wins its independence thanks to a reggae performance at the United Nations by local rebel Delgado (Billy Connolly) who has sworn never to speak until Cascara is free (so he communicates through song). Unfortunately a Running Gag in the movie is Delgado's awful singing, so the Cascarans think they're stuffed until a cameo appearance by George Harrison, Ringo Starr and Eric Clapton save the day.
In Kelly's Heroes, Oddball's tank crew play loud music when they roll out into combat, to psych themselves up as well as confuse the opposition. They're reluctant soldiers at best and hope that their show of bravado will intimidate the enemy so badly there won't be a fight.
Scott Pilgrim goes into a musical power rock battle against Matthew Patel, Todd Ingram and the Katayanagi Brothers.
While Matthew Patel is the only one actually utilising music in the fight (his Bollywood-esque song, "Slick" summoning his Demon Hipster Chicks and revealing his ability to throw fireballs), Scott manages to sufficiently stun Matthew long enough for him to deliver the knockout blow by hurling a cymbal from Kim's drum kit like a frisbee.
Realising that hand-to-hand combat is ineffective against the telekinetic super-vegan Todd Ingram, Scott attempts to resort to a bass guitar battle in order to gain the upper hand; a battle which Todd wins in style by power-chording Scott through the nearest wall.
Against the Katayanagi Twins, Sex Bob-Omb is in an amp-vs-amp rock battle. The Katayanagi's music summons two dragons. Sex Bob-Omb's music summons a giant sasquatch, which proceeds to beat the shit out of both dragons.
The Disney Channel Original Movie Lemonade Mouth is this, but this time, to save a Lemonade vending machine from being removed. They succeeded, and later became rock stars.
A minor example in Cry-Baby, but still funny. The movie is set among teenagers in Baltimore, Maryland, in 1954 - on the eve of public-school integration. The title character, who is the leader of the "drapes," announces that he is about to sing something "colored" - causing the leader of the "squares" to cringe up and shriek.
In the live-action Masters of the Universe movie, Kevin uses his electronic keyboard to open a portal to Eternia, thereby allowed He-Man to return to Eternia and face down Skeletor.
Close Encounters of the Third Kind has the humans finally making contact with the aliens by playing a particular musical sequence (sol la fa fa do, where the second fa is an octave below the first). At which point a human/alien jam begins. It's implied that this is a test of sorts to see if we're worth talking to; as tests go, it's not a bad one.
By the end of Purple Rain, Prince's life has devolved into one hot mess, beset with family trauma, girlfriend troubles, and professional problems in his music career. But, in the final scene, he picks up his guitar and magically uses it to make everything OK again, by turning out a brilliant, masterful, achingly beautiful performance of the title song, ending on a note (literally) of triumph.
At the climax of Lisztomania, Richard Wagner mutates into a combination of Frankenstein's Monster and Adolf Hitler, and he wreaks mass destruction on the world with the dark side of the power of rock, firing a guitar that is a machine gun. Franz Liszt saves the world by blasting off in a fighter jet whose controls are a musical keyboard, and destroys Wagner in an aerial assault with the power of rock, then flies off into heaven singing "Liebesträume."