Being part of the Back to the Beginning festival — Black Sabbath and Ozzy Osbourne‘s final live performances — on July 5 in Birmingham, England, will be special for the myriad musicians involved. But Metallica bassist Robert Trujillo has a different stake in the proceedings.

Trujillo served as Osbourne’s bass player from 1996 to 2003, when he joined Metallica. He co-wrote songs for 2001’s Down to Earth and recorded fresh bass parts for 2002 reissues of Blizzard of Ozz and Diary of a Madman, and introduced his signature, sumo-like “crab walk” stage move while playing Black Sabbath’s “Iron Man” with Osbourne. Trujillo also co-wrote four songs on Osbourne’s Grammy-winning 2022 album Patient No. 9, and played on seven of its 13 tracks. And the bassist was part of the all-star performance for Osbourne’s induction last October into the Rock and Roll Hall of fame.

“I’m always there for Ozz,” Trujillo tells Billboard. “It’s surreal … to go from playing Black Sabbath songs and Ozzy solo material at backyard parties at age sort of 16 and 17, over on the west side of Los Angeles before you went to the clubs … and then once I got on stage with Ozzy when I played in his band, playing songs like ‘Iron Man,’ ‘Sweet Leaf’ and ‘War Pigs’ was so incredible and surreal, like a dream come true. To do that and there he is, in front of me — it was great.

“So this experience we’re about to have in Birmingham is really special, but it’s also sad because you know this is the final show for them, and that’s definite. It feels like the closing of a chapter.”

Trujillo’s connection to Osbourne and Black Sabbath goes back to his childhood, in a manner he says is also shared by his Metallica mates James Hetfield, Lars Ulrich and Kirk Hammett.

“The first music that was heavy that really did scare me came from Black Sabbath,” Trujillo explains. “All of us in Metallica have similar stories. It was listening to the song ‘Black Sabbath’ and looking at that photo of the woman on the [first album] cover, with the church in the background, and scaring ourselves: ‘What is this all about? Who is this woman? Where is this?’ It just resonated with us and scared us as kids.

“It’s so funny we had that similar experience. I thought that was pretty cool.”

Trujillo recalls that during his days in Osbourne’s band, the singer told him about Black Sabbath watching the 1973 film The Exorcist together while on the road in the U.S. “They were so scared by it they slept with the lights on — I don’t even know if they made it through the whole film,” he says. “It was so funny to hear Ozzy tell that story about how frightened they were. He was, ‘Can you imagine the Prince of Darkness, afraid of a movie?!’” he laughs.

“So what they experienced through The Exorcist, we all experienced through the [Black Sabbath] album and their music — especially on that first record.”

Because of that, the Metallica crew will be at Back to the Beginning as much fans as performers.

“We’re very excited to see Sabbath play,” Trujillo says. “It’s also a mystery to see what they’re gonna play and how much they’re gonna be able to do. It’s just cool that so many musicians — young and old and in-between — are gonna be part of this. Everybody’s around to celebrate the right way. It’s like three days compacted into one, and it’s an honor and privilege and really the ultimate sign of respect for that band.”

Trujillo says Metallica was one of the first bands approached to be part of the Back to the Beginning event, whose lineup also includes Guns N’ Roses, Slayer, Tool, Patera, Halestorm, Alice in Chains, Sammy Hagar, Billy Corgan and many more, with Rage Against the Machine’s Tom Morello serving as music director. “We got asked months and months and months ago — six months ago or before, when people didn’t know that it was happening,” Trujillo remembers. “Then I started hearing about it, so it was kind of interesting to see the excitement build with other musicians. It was sort of the talk of the town — at least in L.A., where I live — among the peers, and I’m thinking, ‘Oh, yeah, I know about that …’”

Metallica has been busy crafting its half-hour set for the event, which will include its own songs as well as at least one Black Sabbath track. Trujillo’s not giving anything away, but predicts “I would imagine we’ll play what fans would probably want to hear from a Metallica set, the popular wheelhouse of what Metallica does. And then as far as the Sabbath song, we’ve played a few over the years. We’ve been working on stuff, but we haven’t officially gone in there and really jammed on it, so it’s a work in progress, but I think the fans will be pleasantly surprised and also excited, ’cause we always put our stamp on it.

“It’s also a great challenge for us. I heard James working on some of it yesterday, before the show, off in the distance in our jam room. Ozzy’s vocals are pretty high — especially back in his youth — he was going for those notes, and I think for anybody that’s a bit of a challenge you’ve got to kind of navigate. So, yeah, we’re gearing up for it, probably like everybody right now. Most of the bands are on tour right now, and probably in their sound checks they’re running through one or two of the Sabbath songs, ’cause you want to do it right, y’know?”

The Back to the Beginning concert will be livestreamed starting at 10 a.m. ET in the United States. Tickets are available via Back to the Beginning’s website.

Metallica, meanwhile, recently wrapped up the latest North American leg of its continuing M72 World Tour, which launched during April of 2023. The group heads to Australia, New Zealand and the Middle East starting in November, with another run through Europe slated for late spring and summer of 2026.