Sammy Hagar joked with the crowd. James Hetfield got real. Billie Joe Armstrong and Pat Monahan had everyone singing along.

The stars charmed in very different ways during the Acoustic-4-A-Cure benefit concert on Thursday at the Fillmore in San Francisco. Yet, they all added something to the equation, resulting in a very enjoyable evening of music.

The fundraiser, which organizers plan to make an annual event, was Hagar’s brainchild. The Bay Area’s famed Red Rocker, who was enshrined into the Rock and Roll Hall of Fame as a member of Van Halen in 2007, was looking for a way to support the Pediatric Cancer Program at UCSF Benioff Children’s Hospital.

So, he decided to do what he does best — have some fun. He called up a few of his talented friends, enlisting Metallica’s Hetfield first in the cause, and organized a musical party at San Francisco’s most legendary rock hall.

The mood was joyous, with the smiles onstage reflected back from the capacity crowd. The vibe was informal and relaxed, so unlike some all-star gatherings. It did indeed feel like a party, although one that was about so much more than just music.

It was also one of the season’s hottest tickets. One look at the lineup and you can figure out why. Besides Hagar and Hetfield, the bill also featured Green Day’s Armstrong, Train’s Monahan, guitar wizard Joe Satriani, Heart’s Nancy Wilson and other artists.

It was Hagar’s party, which meant he could’ve demanded to go on last. Instead, he said he decided to organize the sets by “age before beauty.”

“I go on first,” he said.

He kicked off the two-hour show with a four-song set that included such nuggets as “Red Voodoo” and “Dreams.” Singing isn’t really this singer’s strong suit, yet he was still fun to watch onstage, joking with the crowd and coming across like someone you’d want to invite to your next barbecue.

Wilson, who took the stage next, is better known for her guitar work than her singing — and for good reason — so she called some other voices to help her out, notably Lauren Larson, lead singer of the Texas rock trio Ume, who joined Wilson for a solid version of Neil Young’s “Hey Hey, My My (Into the Black).”

Monahan delighted the crowd with singalong renditions of Train smashes “Drops of Jupiter (Tell Me),” “Hey, Soul Sister” and “Drive By.” He was joined by Hagar for a tuneful rendition of “Ramble On,” the Led Zeppelin classic that has long been a part of Train shows.

The highlight was Hetfield’s set, which was equally poignant and powerful. As the frontman for the world’s greatest metal band, Hetfield might seem like an unlikely candidate to go acoustic. Yet, he proved entirely capable and comfortable in the setting, thrilling with Metallica’s “Nothing Else Matters” and a cover of the Beatles’ “In My Life.” He gave us a peak into his personal world, describing how the death of his parents from cancer inspired the touching Metallica number “Until it Sleeps.”

Hetfield then invited Armstrong on stage for what would be the evening’s definitive moment. The former began playing a chilling version of Bob Seger’s “Turn the Page,” which Armstrong took and transitioned into Green Day’s “Boulevard of Broken Dreams.” They traded verses — going back and forth between the two songs — while Satriani accompanied them on guitar. It was the type of magical medley that fans dream of getting — but so rarely do — at these kinds of all-star concerts.

Armstrong closed the main set by performing a fan-friendly mix of Green Day favorites as well as a superb cover of The Replacements’ “Bastards of Young.” The show closed in fine fashion with, of course, an all-star jam, bringing the entire cast of players out to the stage for a fun run through Bob Dylan’s “Rainy Day Women #12 & 35.”

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