A snarling punk band should be able to excite in even the dullest venue, yet it's still rather hard to get excited about a gig billed as appearing in – as Meltdown festival's website puts it – a "foyer".

You can't imagine people claiming, decades later, that they were present at the fabled 2014 foyer show. The Sex Pistols' legend could never have been born in a foyer.

As it turns out, James Lavelle's Meltdown is savvier than that, and they've actually put the Missouri band of brothers Radkey in the arts venue's concrete basement. There's a makeshift bar, an impressive lighting rig and, every now and then, a whiff of pee. It's perfect for the breakneck YA trio, whose Misfits-indebted riffs are as fast, furious and flashy as a 1970s Dodge with Vin Diesel at the wheel, and who could play a Bonmarché shop floor and make it seem like the show of their lives.

Tonight, the siblings have a telekinetic tightness that can only come from years of sharing the same bedroom and now – following two EPs, a UK tour with Drenge and an appearance on Jools Holland last year – months sharing floors on the road. Dee (20, guitar, furrowed brow) has a doom-croon that flares into screams in the same breath, not unlike Glenn Danzig's theatrical baritone. Isaiah (18, bass, denim waistcoat) is the rock posturing, wisecracking showman. And Solomon (17, drums, Weezer fan) keeps everything surging forward with eviscerating thuds.

At times, it's easy to forget how young they are. That is, until Isaiah starts enthusing about the new Batman costume, or introduces barbed punk ripper Romance Dawn as "a slow dance number about fucking shit up with a baseball bat". It can come off a bit like Tom and Jerry hardcore – their politics are those of teenage boys who watch cartoons and play video games. But anti-racism anthem NIGGA (Not OK) and new track Feed My Brain ("about a teacher that fucks a student") show they can add seething social observation into the power-punk mix. A legend hasn't been made tonight but their future sure looks rad.