Japanese metal idol band Babymetal were joined onstage by rock legend Chad Smith of Red Hot Chili Peppers in London on Sunday while the teenagers were on tour in the U.K. Smith took the stage for a couple of songs, replacing Babymetal’s usual drummer Hideki Aoyama where the group performed a cover of Judas Priest’s “Breaking The Law,” and several other songs by Priest. Then in a sincere moment for the whole venue, Smith began to sing a personal happy birthday song to singer Su-Metal before leaving. The entire experience was undoubtedly a pleasant surprise for unexpecting fans who never expected to see the rock legend alongside one of their favorite bands in an epic collaboration. Check below to watch the videos.

The Japanese rockers were prepared as ever to perform those Judas Priest covers, because prior to London’s show, Babymetal was able to with Rob Halford, one of the Judas Priest’s band members. Click here to watch the video.

Earlier this month Babymetal announced they’d be joining another iconic rock band, Guns N’ Roses, when they make their way to Japan on tour. Before the year’s end, the band is expected to release a new live album at Wembley so make sure to keep your eyes peeled for the upcoming project.

Earlier this year, the band caught some unintended heat online when Rob Zombie posted a picture hanging out with the trio and recieved backlash on Facebook from internet haters for not being real metalheads. They were quickly shut down when Zombie defended them, noting the amount of energy they have and their badass credentials.