If someone were to ask you to name the biggest thing in metal music now, would you answer: a) a bunch of hirsute Australian men growling about hellfire and blood; b) a bunch of hirsute American men growling about hellfire and blood; or c) a trio of Japanese teenage girls in froufrou skirts who do twirling dance routines and sing sugary pop melodies over thrash metal? It is, of course, the third: headbangers worldwide are having the leather pants charmed off them by a fusion of styles that could only come from Japan.

Babymetal are the pioneers of kawaii, or "cute", metal. You can think of them as Hello Cannibal Kitty and their music as the lost soundtrack to the Japanese Hunger Games precursor, Battle Royale. A typical song, Awadama Fever, interlaces slabs of angry guitar and undanceably fast breakbeats, while the girls squeak about "bubble ball fever" and chewing gum.

The iron maidens of Babymetal (left to right) Yuimetal, Su-metal and Moametal.

The bizarre combination is striking a power chord with fans of heavy metal worldwide. In April, the band released its second album, Metal Resistance, to glowing reviews and a top 10 chart place in Australia, and played a sold-out gig at Britain's Wembley Arena, the first Japanese act to do so. They broke the arena's record for merchandise sold, and in Japan 12,000 fans trooped to cinemas at 4.30am to watch live screenings of the gig.

So-called idol bands – manufactured pop groups – are huge in Japan. It was the genius of a man who calls himself "Koba-metal", a producer with the Japanese talent agency Amuse, to spot that what the rock world needed was a metal Mickey Mouse Club. As he points out when I meet him and the band in the K West hotel, in west London, you can't imagine Metallica or Iron Maiden doing synchronised dancing on stage.