(aka: When Legends Gatecrash the Stage and Blow Our Socks Off, Mun)

Let’s be honest, there’s nothing more glorious than a surprise guest crashing a rock gig or metal set. You’re vibin’ in the crowd, sipping warm lager, and suddenly—BOOM! Slash walks on. Halford belts a note. Dave Grohl appears like some drum-wielding wizard from the fog.
It’s enough to make your past self say, “What the ACTUAL hell is occurring?!” 🤯

We’ve compiled 12 of the most legendary guest performances to ever grace stages and studios—those “did that really happen?” moments that live rent-free in our minds (and playlists). Strap in, c’mon butt, we’re going in loud!

🥉12. Brian May Joins Foo Fighters – Wembley Stadium, 2008

🎸 Track: “Tie Your Mother Down” (Queen cover)

The Foo Fighters were already tearing up Wembley like it was their backyard BBQ. Then out stroll Brian May—axe in hand, hair like a lion, ready to melt faces. Roger Taylor jumps on drums, and suddenly we’re in full-on Queen mode. Hawkins called Brian “the greatest guitarist of all time”—and he wasn’t wrong, was he?

Moment of madness: When Hawkins, Grohl, May and Taylor took over that stadium, it stopped being a concert and started being a royal coronation in rock.

🥉11. Slash with Michael Jackson – 1995 MTV VMAs

🎩 Track: “Black or White” / “Beat It” mash-up

This one had the energy of a bad idea… but delivered like a fever dream. Slash busts in with THE guitar tone, looking like he just fell out of a Guns N’ Roses tour bus and nailed the solo anyway. MJ moonwalks around him. It’s like Chuck Berry and Broadway had a baby.

Iconic because: No one expected Slash to be upstaging the King of Pop, but that Les Paul spoke louder than words.

🥉10. Bruce Dickinson Joins Halford and Geoff Tate – Rock in Rio, 2000

⚔️ Track: “The One You Love to Hate”

This wasn’t a guest spot—it was a vocal battle royal. Three of metal’s mightiest frontmen screaming their lungs out together? Yes, please. Bruce soared like a Spitfire. Halford shrieked like a banshee. Tate crooned like a pissed-off phantom.

Goosebump level: Nuclear. This was a rare holy trinity of vocal power that had mosh pits collectively saying, “I need a sit-down.”

🥉9. James Hetfield & Lars Ulrich with Mercyful Fate – San Francisco, 1993

🕯️ Track: “Return of the Vampire” & “Satan’s Fall”

If you were in that crowd, you hit the black metal jackpot. Hetfield on vocals. Ulrich pounding the kit. King Diamond cackling like a demonic opera villain. It was evil, it was epic, it was underground history in the making.

Only in San Fran, mun… This kind of metal magic don’t just happen anywhere.

🥉8. Ronnie James Dio with Tenacious D – Madison Square Garden, 2006

🌈 Track: “Dio”

You write a tribute song to a metal god… then the metal god shows up to sing it with you? Dio joined The D live, and it was like Gandalf had entered the pit. The power, the vocals, the sheer cheek of it. Glorious.

Shout it with us: “DIOOOOOOOO CAN YOU HEAR ME?!”

🥉7. Axl Rose Joins AC/DC – Rock or Bust Tour, 2016

⚡ Track: Entire tour

When Brian Johnson had to step back, fans feared the worst. But Axl bloody Rose showed up, sat his broken leg on Dave Grohl’s borrowed throne, and absolutely belted through the AC/DC catalogue like he’d been born in a coal mine. The world expected a trainwreck—and got a thunderous resurrection.

Result: The snarl of GNR met the stomp of AC/DC, and it was beautiful mayhem.

🥈6. Eddie Van Halen’s Solo on “Beat It” – Michael Jackson, 1983

🎚️ Track: “Beat It” (studio recording)

It’s the solo. The one that made kids want to pick up a guitar and play until their fingers bled. Eddie reportedly did it for free and blew the roof off one of the biggest pop songs of all time. You can thank him for every pop-metal crossover that followed.

No Eddie = No “Beat It” as we know it. Absolute fact.

🥈5. Rob Halford Joins Babymetal – AP Music Awards, 2016

🦊 Track: “Painkiller” / “Breaking the Law”

The Metal God meets Japan’s kawaii-metal queens. On paper, it sounds insane. On stage? It was glorious chaos. Halford headbanging with choreographed schoolgirls in leather and spikes. The crowd looked confused—and then completely sold.

Proof: Metal has no borders. Just riffs.

🥈4. Lemmy with Foo Fighters – VH1 Rock Honors, 2006

⚰️ Track: “Shake Your Blood”

Lemmy didn’t do “guest spots” – he conquered. When he joined Foo Fighters for this knuckle-dragging banger, he didn’t just front the band—he owned the whole damn stage. Growling through the mic like a warlord on bourbon.

Lemmy’s rule: Show up, plug in, shake the planet.

🥈3. Dave Grohl Drums for Queens of the Stone Age – Songs for the Deaf, 2002

🥁 Track: Entire album

If drumming had a cheat code, Dave Grohl is it. On this cult classic, he wasn’t a guest—he was an avalanche. Every fill, every thump, every swing of the sticks made this album iconic. Grohl made drums sexy again. Fact.

Start with: “No One Knows.” Then keep going until your neighbours complain.

🥈2. Freddie Mercury & David Bowie – “Under Pressure”

🌍 Track: Studio & rehearsal

Did they perform it live together often? Nah. Do we care? Absolutely not. Because the song and the rehearsal footage are immortal. Freddie’s fire. Bowie’s cool. It’s two titans circling each other, daring the other to go harder. And they did.

Literal pressure: They wrote it in one night. That’s not just genius—that’s criminally smooth.

🥇1. Metallica & Lady Gaga – Grammys, 2017

🔥 Track: “Moth Into Flame”

Yes, the mic cut out. Yes, James Hetfield got tamping and kicked a mic stand. But this? This was iconic. Gaga proved she could hang with the biggest metal band in the world—and then some. The fire. The hair flips. The unapologetic swagger. People laughed. People complained. But it ruled.

Rock n’ roll rule #1: When things go wrong, crank it harder. Gaga did just that.

🏅 Honourable Mentions

  • Elton John x Ozzy – “Ordinary Man” (the soft side of darkness)
  • Chris Cornell with Linkin Park (tears guaranteed)
  • Dimebag posthumously on Nickelback’s “Side of a Bullet” (weird, but powerful)
  • Corey Taylor + Apocalyptica – “I’m Not Jesus” (strings + screams = lush chaos)
  • Tom Morello on everything – seriously, pick a track, he’s on it.

🎤 Final Riff:

Guest spots aren’t just “nice extras.” They’re earth-shaking, crowd-pleasing, history-making moments that make rock ‘n’ metal the glorious mess it is. Whether it’s Dio turning up for a laugh or Gaga melting faces at the Grammys, these crossovers are the lifeblood of the scene. They keep it mad, loud, and proper tidy.

So next time you’re at a gig and someone unexpected walks on stage, just do what we all do:
👇
Throw your horns up, lose your voice, and yell—

“YESS MUN, GET IN!”

🎸 Got a favourite guest spot we missed? Shout about it in the comments below or tag us @theriffreportuk on socials. Diolch for reading, legends! 🤘🔥