Devil horns: the universal symbol for heavy metal worship. Join finger and thumb to make a snout and that hand gesture becomes a fox shadow-puppet to throw at the shrine of Babymetal for the fox god, who according to the band, delivers them the music to share with the world. Tonight, that symbol is held aloft by meaty metalheads, under-fives and kawaii girls for more than an hour and a half.

In 2014, Babymetal hype reached UK shores and landed them a headline show at the Forum in London. Later that year they stepped up to Brixton Academy, and now, much to everyone’s disbelief, they are filling Wembley Arena. The curiosity and novelty of checking out a metal J-pop band fronted by three teen girls in tutus has passed. This isn’t another metal gimmick: it’s a legitimate phenomenon.

Their set reveals itself as an astonishing grey church while the girls rise from a vertical platform lift to war cries of “Babymetal desu”. Within seconds of entry, they’re snapping into cheering come cybergoth raving and their very special version of headbanging – a pendulum swing forward, ponytails delicately thrashing.

Freshly minted second album Metal Resistance provides plenty of new material, including a solo power ballad led by band member Su-Metal wearing a cape. It’s Eurovision with speed metal interludes – in the best way imaginable. Later in the set, narration screens inform us that Yuimetal and Moametal have been turned to the dark side by Death Vader (because why not?).

Facebook Twitter Pinterest International appeal … Babymetal. Photograph: Taku Fujii

There is no longer anything about them that seems ridiculous. The band are tight and there is spotlit time enough for wailing solos and breakdowns. Given this versatile space and production budget, slick dance routines and the blending of every genre from trap to bubblegum pop suddenly makes perfect sense. The group are a true product of idol culture, each pristine girl present to see us just as much as the 12,000 of us are there to worship them. The adoration is radiating from every bloke with a tear in his eye.

The grand finale: the glittery trio revolve at the end of the walkway among their fans. It’s euphoric. Their mission statement to bring metal to the world is repeated at every live show. Considering their venue and the presence of non-metal fans and flags from at least 10 different countries at the show, which is also live-streamed to Japan, it looks as if they’re getting close. Metal resistance is futile.

• This article was amended on 3 and 5 April 2016. An earlier version said that Babymetal performed at Brixton Academy last year. They performed there in November 2014. In addition, it referred to Darth, rather than Death, Vader.