It's not surprising that Babymetal has gone viral. The trio, bringing the seemingly disparate worlds of idol pop and heavy metal together, is a visually striking project perfect for the "weird Japan" fans on the Internet.

What's surprising, however, is seeing Babymetal's eponymous debut top the iTunes heavy metal charts in the United States, Canada and Britain — and climbing as high as No. 35 on the American iTunes album chart. Sonically, Babymetal should be one cool idea driven into the ground — how many songs merging cutesy choruses with guttural shrieks can a headbanger take? — but the project boasts just enough musical diversity to make for a good listen.

The dominant sounds throughout "Babymetal" are power chords, breakneck drumming and throaty howls offset by cheery singing, and the group lags when sticking strictly to that combo. However, many of the tracks make subtle changes to keep the album humming along. "4 no Uta" zips from guitar workouts to tropical lounge interludes, while "Ii ne!" takes a breather for a group rap that sounds like it has been ripped from the once-hip witch house subgenre. The lyrics focus on typical idol-pop topics — chocolate, the struggle of waking up — but also spin into subjects such as bullying and, on "Onedari Daisakusen," tricking your dad into giving you money.