Yes, the video above is for a heavy-metal song, with pop and dubstep inflections. Yes, the band performing that song comprises three teenage girls wearing matching cutesy-goth outfits and not playing any instruments. Yes, the song is actually about wanting to eat chocolate (and, apparently, worrying you’ll get fat from it). And yes, it’s real — and, more than that, it’s a bona fide hit. This video has 5.8 million YouTube views and the eponymous debut album from the band, Babymetal, which was released in February, is at No. 4 on iTunes’ Japanese rock chart and has recently cracked the Billboard 200.

Now, however, Babymetal faces a test: it’s been announced that they’ll be playing at this year’s Sonisphere, a British metal festival. Sonisphere’s line-up is no joke — we’re talking bands like Iron Maiden and Limp Bizkit and Alice in Chains — and the gig will also be Babymetal’s first time in the U.K.

So can the group win over actual metal fans?

It’s a bit of an odd question, because Babymetal isn’t exactly trying to blend in with the metal mainstream. Their official Twitter bio makes it clear that the intention is to be “kawaii,” or cute, by mixing metal and Japanese pop. There’s no real illusion that these girls are into rock because it’s the only way to unleash their inner rage, and — despite their genre of choice — they’re no less manufactured than any other J-pop group. The lead singer goes by Su-Metal; then there’s Yuimetal and Moametal, whose instruments are listed as “Scream, Dance”; they’re also an off-shoot of a non-metal pop band, Sakura Gakuin. (Sakura Gakuin has a very specific concept, which is that when a girl graduates from middle school she’s too old to participate. Though Babymetal’s lead singer graduated from the other group last year, Babymetal’s members aren’t too far removed from baby-dom; the other two are just 14.)

Babymetal has already demonstrated that they can play big shows back at home, as they’ve sold out Tokyo’s Budokan arena multiple times, but when it comes to the rest of the world, there’s a difference between being a one-off “ridiculous” oddity and being a band that can make it last on a global-scale. By now, the pop sounds of Japan (and J-pop’s cousin, K-pop) are familiar enough to global listeners that the songs can be judged on their merits rather than merely as “wacky” imports. But Babymetal’s music hasn’t reached that stage yet, so the jarring juxtaposition of their image and sound is enough to get people paying attention for now — but that won’t last.

Whether they can impress metal-heads (or, instead, draw enough of their own fans to Sonisphere that that’s unnecessary) will be a major clue about which direction they’re heading. In the mean time, they’ll be busy headbanging.

Write to Lily Rothman at lily.rothman@time.com.