Fall Out Boy, Hammersmith Palais, London <!-- none onestar twostar fourstar fivestar -->

The teenager to my right - with his camera phone and his four quid bottle of Foster's and his mum waiting at the back to pick him up at the end of the gig - said Fall Out Boy are "like, third-generation emo". Really? I thought they were "proto-punk" or "pop punk" or "indie punk", or whatever you call a band that sounds like the bastard progeny of Beefeater, My Chemical Romance and Busted. Before I could take issue with the young Polonius, though, Fall Out Boy launched into a patchy, if spunky set.

Their line-up is confusing. Patrick Stump, the singer and lead guitarist, looks anything but a front man. With his trucker cap slung low over his eyes and his tracksuit top and his bashful manner, he might be selling fries at a drive-through. Which is presumably why he leaves the talking to Pete Wentz - the good-looking, skinny boy on bass.

Then there's Joe Troh-man, who, depending on how charitable you are feeling, looks either like a Blonde on Blonde-era Dylan or Sideshow Bob. But most extraordinary of all is Andy Hurley, the Zeppelin-wannabe who seemed to be playing the drums naked (or, if he wasn't, his shorts were snug enough to be obscured by the snare drum).

Still, the soon-to-be-defunct Hammersmith Palais was packed to its creaking rafters, and Fall Out Boy delighted a thousand camera phones. Stump may not be much of a talker but his voice suits the baroque material, and, with the sound of fusing metal all around him, belies his shy persona by nailing tricky vocal lines. Wentz, meanwhile, has real front, and it's clear which one of the band the hundreds of teenage girls in the audience have come to see.

"We have the poor fortune of being a shitty live band," admitted Wentz at the beginning, but he's being a little unfair. Their playing is not always spectacular - the two guitarists sounded, occasionally, like they were listening to different drummers - but what Fall Out Boy lose in accuracy they make up for in punch. If you can forget, momentarily, the facile lyrics on almost every track, there were some good moments - the new single, "This Ain't a Scene, It's an Arms Race", might be about Iraq, or it might be about the emo scene, or neither, it's not very clear, but it does at least contain a rousing chorus.

The Fall Out Boy tour resumes in the UK on 31 March (see www.falloutboyrock.com)