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.

"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"

Green Day and Billie Eilish performed together, Billy Crystal spoke of the pain of losing his home in the fires, and Joni Mitchell gave a rare performance.

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.

Rod Stewart, Billie Eilish, the Red Hot Chili Peppers and Lady Gaga are among a star-studded set of musicians performing at a benefit concert later this month for wildfire recovery and relief, organizers announced Thursday.

A cavalcade of enormous rock and pop stars, old and new, will perform at a benefit concert in Los Angeles, and streamed around the world.

A range of upcoming musical events will aim to provide relief funds for those impacted by the Eaton and Palisades wildfires.

The concert will also be screened live at select AMC Theatres and and Regal Cinema locations in the U.S. If you will be on the move, iHeartRadio, the national audio partner for the event, will also feature the FireAid concert across over 860 radio stations in the U.S., digital platforms, and the iHeartRadio app.

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.

Anderson .Paak and Dr. Dre performed "Still D.R.E" and "California Love" at the FireAid Benefit Concert for Los Angeles. Get the details.

Green Day opened up the benefit concert and were quickly joined by Eilish for a performance of the band’s “Last Night on Earth” from their 2009 album “21st Century Breakdown.” Eilish departed the stage after the duet and Green Day continued with “Still Breathing” and “When I Come Around.”