Coachella fans rocked out on Saturday to pop-punk headliner Green Day following a blockbuster cameo from US senator Bernie Sanders, who had the massive crowd roaring as he urged against political apathy.

Also among the A-list performances on day two of the California music festival was Charli XCX, whose club-ready ode to her sensational year included cameos from Billie Eilish, Lorde and Troye Sivan.

She bathed the desert in her signature "brat" lime green to close out her electric set that sent her audience into exultations, especially when she brought out Eilish to perform their lip-biter of a song "Guess."

Green Day's career-spanning performance filled more than 90 minutes with hits — including "Brain Stew," "Minority," "Basket Case" and "When I Come Around" — a reminder of the grip the rockers had on popular music throughout their 1990s and 2000s heyday.

The band opened with "American Idiot," the lead single off their smash album of the same name that took direct aim at the George W. Bush administration — and whose lyrics Billie Joe Armstrong adapted to the present day.

"I'm not part of the MAGA agenda," he sang to deafening cheers, referring to President Donald Trump's "Make America Great Again" movement.

That was the group's most overtly political statement of the night, though Green Day's music is already a political statement in itself.

And in case that was unclear, Armstrong prefaced the song "Holiday" with the obvious: "This is an anti-war song."

But it was Sanders who truly brought politics to the desert, making an unbilled pit stop following his tens-of-thousands-strong Los Angeles "Fighting Oligarchy" rally earlier in the day.

As he was introduced at the Outdoor Stage within minutes of Charli XCX's closing song, festival-goers rushed over to see the self-described socialist.

"You can turn away and you can ignore what goes on but if you do that, you do it at your own peril. We need you to stand up, to fight for justice. To fight for economic justice, social justice, and racial justice," Sanders told the rapt crowd.

Dudamel takes the desert

Brazilian DJ Alok packed his massive tent for a show demanding to "Keep Art Human" as the arts are threatened by the rapid proliferation of artificial intelligence.

"To create art, you need the soul," he told AFP following the set.

Gustavo Dudamel meanwhile led the Los Angeles Philharmonic in a sweeping sunset show that turned the concept of genre on its head, marrying orchestral arrangements with elements from just about every musical form.

Country star Maren Morris, Icelandic jazz-inspired pop singer Laufey, Argentine rap duo Ca7riel & Paco Amoroso, LA's own Becky G, DJ and producer Zedd — all joined Dudamel and the Phil onstage.

And LL Cool J served as the rollicking performance's exclamation point, as he, Dudamel and the orchestra melded "The Imperial March" from "Star Wars" with the superstar rapper's "Rock the Bells."

"Werk!" exclaimed one audience member as Dudamel's kinetic movements were projected behind his orchestra.

Other features on Saturday included Japanese Breakfast, The Original Misfits and rapper Travis Scott, whose late-night set left some fans exasperated after he began around 20 minutes behind schedule.

On deck Sunday are headliner Post Malone, hip-hop superstar Megan Thee Stallion, Best New Artist Grammy nominee Shaboozey and German electronic pioneers Kraftwerk.

Coachella's second weekend — which features the same lineup, save for cameo shakeups and occasional special features — will take place April 18-20.