Adam Lambert first performed with Queen on the 2009 season finale of American Idol, but it wasn't until nearly a year and a half later that he made his debut as their singer, albeit in an unofficial capacity.

The show took place on Nov. 6, 2011, at the MTV Europe Music Awards in Belfast, where, earlier in the evening, Queen received the Global Icon Award. They performed three songs with Lambert, "The Show Must Go On," "We Will Rock You" (with the bass line from "Under Pressure" in the introduction) and "We Are the Champions," the latter a reprise from the earlier Idol performance. (You can see photos from the show below.)

The seeds had unknowingly been planted during Lambert's audition for American Idol, when he sang "Bohemian Rhapsody." As Brian May recalled, Queen were looking for a new singer after ending their four-year association with Paul Rodgers. It all coincided perfectly with Lambert's rendition of the Queen classic.

"I had thousands of people send me the video saying, 'You have to see this guy!'" he told Yahoo! "So it immediately put [him] in there. And then we came to see [Lambert perform]. That's where it began."

The performance on the Idol finale led to the inevitable rumors that Lambert received an offer to join the band. For his part, May denied them, but admitted that he and drummer Roger Taylor were seriously interested in the 27-year-old singer from San Diego.

“Amongst all that furor, there wasn’t really a quiet moment to talk,” May told Rolling Stone. “But [Roger] and I are definitely hoping to have a meaningful conversation with him at some point. It’s not like we, as Queen, would rush into coalescing with another singer just like that. It isn’t that easy. But I’d certainly like to work with Adam. That is one amazing instrument he has there.”

A few weeks later, Taylor told UCR that Lambert had "really matured and has become an incredible performer. I think Brian and I will very possibly be doing something with Adam, because he’s really great. His range is unequaled, I think, and his stage presence is really quite something these days."

Two months later, they made it official when Queen + Adam Lambert announced a small summer tour of Europe. Lambert made it clear from the start that he wasn't looking to fill Freddie Mercury's shoes.

“The intention is to pay tribute to Freddie and the band by singing some fucking great songs," he said. "It’s to keep the music alive for the fans and give it an energy that Freddie would have been proud of. There's no intention in my mind of replacing Freddie. That's impossible. The way I’m choosing to view it is that it’s a great honor and one I’m in no way going to shirk."

The tour kicked off on June 30, 2012, in Kiev as part of an AIDS benefit that also featured Elton John. Even though they performed 25 songs, Lambert sang on only 18 of them, with May taking the lead on three and Taylor singing two, plus a solo spotlight for May and drum battle between Taylor and his son, Rufus. (You can see the set list for the show below.)

Lambert later revealed that he was nervous for those first shows, but the support of the band and the audience carried him through. “I thought, ‘There’s no way I should be doing this,'" he said. "I had the confidence of the band and they were really lovely about it. They were like, ‘No, no, no, you’re great. We love it. Do what you want.’ But in my head I kept going, ‘No, I don’t know.’

“The first audience we had was very supportive, and each audience afterwards was supportive. So, slowly, little by little, I was like, ‘Okay, all right, I can do this – kind of.’ But there’s no comparing to Freddie.”

They made their U.S. debut a year later with an abbreviated set at the iHeartRadio Music Festival in Las Vegas and mounted a full-scale North American trek in 2014. By then, the May and Taylor vocal spotlights had been removed. They've toured the world regularly ever since, including a second North American jaunt in 2017 and a Las Vegas residency in 2018. A return to North America, the Rhapsody tour, was slated for summer 2019.

Still, Lambert hasn't recorded with Queen, though both May and Taylor have spoken about the possibility of that happening. "If we do anything in the future, I'd like it to be something new," Taylor said back in 2016. "I don't know how new it would sound, but I think if Brian could come up with a song or two which we felt sort of fitted."

Throughout his tenure, Lambert has retained a public profile as a solo act. His second solo album, Trespassing, arrived in 2012, a month before the Kiev date; he followed it up with 2015's The Original High. He supported both records with world tours.

He's also made numerous appearances as a judge or mentor on competition shows, including a return to American Idol in 2014, and had an uncredited role in Bohemian Rhapsody as a trucker waiting for Mercury (played by Rami Malek) to end a phone call so the two can have an illicit tryst.

Lambert, who came out in 2009,.has also used his fame to advocate and raise money for LGBTQ issues, and has won numerous awards from LGBTQ organizations for his activism and philanthropic efforts.

Queen + Adam Lambert June 30, 2012, Kiev
1. "Seven Seas of Rhye"
2. "Keep Yourself Alive"
3. "We Will Rock You"
4. "Fat Bottomed Girls'
5. "Don't Stop Me Now"
6. "Under Pressure"
7. "I Want It All"
8. "Who Wants to Live Forever"
9. "A Kind of Magic" (Roger on lead vocals)
10. "These Are the Days of Our Lives" (Roger on lead vocals)
11. "Love of My Life" (Brian on lead vocals)
12. "'39" (Brian on lead vocals)
13. "Dragon Attack"
14. Drum Battle
15. Guitar Solo
16. "I Want to Break Free"
17. "Another One Bites the Dust"
18. "Radio Ga Ga"
19. "Somebody to Love"
20. "Crazy Little Thing Called Love"
21. "The Show Must Go On"
22. "Bohemian Rhapsody"
23. "Tie Your Mother Down" (Brian on lead vocals)
24. "We Will Rock You"
25. "We Are the Champions"

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