Expectation has been mounting since the Irish rock group gave strong hints last week about “special guests” joining them at their two rescheduled Paris gigs.
U2 had been due to play on November 14 and 15, but the gigs were cancelled after the shootings and suicide bombings that left 130 people dead.
There has been no official confirmation that the Eagles of Death Metal will appear, despite fevered speculation on social media.
Deepening the mystery, it was singer Patti Smith that joined U2 for the last song of Sunday night's concert at the packed 16,000-capacity AccorHotels Arena.
Just before the show, the band management said “some people have been saying that Eagles of Death Metal will appear on stage with U2 tonight. This is not the case.”
The statement, however, did not rule out an appearance by the California rockers on Monday night, and sources were still suggesting they would appear for the finale of the concert, which will be broadcast on US cable channel HBO.
'Vive la France!'
“Vive la France!” U2's lead singer Bono roared as he walked out on stage for Sunday's night's concert.
“Tonight, we are all Parisians. If you love liberty, then Paris is your hometown,” he added in a mixture of French and English to rapturous applause.
But the emotional high-point of the show came at the end after Smith had joined the band for a rousing version of her song “People Have The Power”.
As the lights went down a giant screen was lit up in the red, white and blue colours of the French flag carrying the names of the 130 victims of the attacks, as Bono sang a part of Jacques Brel's standard “Ne me quitte pas” (Don't Leave Me).
Earlier the U2 frontman revealed he had written a song about attacks, the worst of which saw 90 people killed by gunman in the Bataclan music venue just as the Eagles of Death Metal began to play.
Bono recited lyrics from “Streets of Surrender” in an interview with CNN, saying he had started writing the song for Italian singer and long-time friend, Zucchero.
“Every man's got one city of liberty, for me it's Paris, I love it,” the song goes.
“Every time I get lost down these ancient streets, I find myself again. I didn't come here to fight you. I came down these streets of love and pride to surrender.”
The song also touches on the refugee crisis, with a lyric mentioning the young Syrian boy photographed dead on a Turkish beach earlier this year.
The band's guitarist The Edge said in the same interview that the group's decision to return so quickly to Paris was a symbolic act of resistence.
“I think we're actually starting the process of resistance, of defiance against this movement,” he said, referring to the Islamic State group that carried out the killings.
U2 said they tried to help “our fellow troubadors” Eagles of Death Metal in the aftermath of the killings, getting them mobile phones, psychological help, and putting a private jet at their disposal.
Meanwhile, Jesse Hughes, the lead singer of the Californian group, who wants the band to be the first to play the Bataclan when it reopens next year, has raised eyebrows in France with his vehement opposition to gun control in the US and support for Donald Trump, the controversial Republican contender for the White House.
A documentary about the colourful singer, “The Redemption of the Devil”, was pulled from the Amsterdam film festival last month in the wake of the killings.
In the film, the singer, who is also a priest in the Universal One Church, brandishes various firearms as he jokes with friends.