A Plurk buddy posted a music video of this band weeks ago and it got me hooked. Japan always have its way into doing weird things & stuff and this is one of them. The band's name is Baby Metal, with the music genre they call Kawaii Metal. According to Wiki, "The group was initially formed as a subunit of the female idol group Sakura Gakuin under the concept of a "fusion of metal and idol [music]" They were founded in 2010 and is currently managed by the Amuse talent agency.
To give detail on their musical style, here is a video of one of their live performances.