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The Amazing Spider-Man 2 star can be seen wearing a blonde wig, white dress and pink eye mask as he strolls through a chanting crowd, looking dazed and confused.
The crowd scene was shot during the indie band's set at Coachella's second weekend last month and is interspersed with snippets of a troubled Garfield shaving his head in a mirror and crying.
Frontman Win Butler spoke out in support of gay rights before performing "We Exist" from latest album Reflektor, about a young man coming out to his dad.
"The right to marry anyone you want is a human rights issue," he told fans.
Butler had previously argued that "it's one of the darker tendencies of humanity to think everyone should fit into a mould".
The full video is expected in the next few weeks, at a time when Garfield is in the limelight. The Bafta-winning actor, 30, hosted Saturday Night Live last weekend and took part in a Spider-Man kiss spoof with Coldplay's Chris Martin.
Last month, Garfield was called out on sexism by none other than his own girlfriend, co-star Emma Stone. When asked how Spider-Man made his iconic costume, Garfield replied: "He sewed it. It’s kind of a feminine thing to do but he really made a very masculine costume."
Stone was unimpressed, prompting her partner to back-track into an awkward ramble about how "we all have feminine in us".