Billie Joe Armstrong and Billie Eilish. Green Day got things started at the Kia Forum, where they surprised fans with Eilish to help them perform, "Last Night on Earth" from 2009's 21st Century Breakdown.

"From the bottom of our hearts, we love you Los Angeles," Billie Joe Armstrong told the crowd, "and we've got your back no matter what"

Billie Eilish made a surprise appearance on stage with Green Day on Thursday to kick off one of two star-studded concerts in Los Angeles put together to raise funds for people affected by deadly wildfires in California this month.

FireAid, featuring Billie Eilish, Lady Gaga, Sting, Red Hot Chili Peppers and others in a fundraiser for Los Angeles-area wildfire relief efforts, is the latest event to combine music and philanthropy.

FireAid benefit concert, Lady Gaga left her mark by debuting a brand-new song written with her fiancé, Michael Polansky, for the victims of the Los Angeles wildfires. "Me and my friend Michael - my fiancé,

Mikael Wood and August Brown are at Inglewood's Intuit Dome and Kia Forum for the FireAid benefit concerts starring Billie Eilish, Lady Gaga, Green Day and Stevie Wonder, among many others.

Lady Gaga wowed the crowd at the FireAid benefit concert with a spellbinding new track. The new song, titled All I Need is Time, was co-written with her fiance Michael Polansky. After engaging fans with her famous hits Shallow and Always Remember Us This Way,