Kai Michael Hansen is a German musician who is the founder, lead guitarist and vocalist of power metal band Gamma Ray. He is also one of the co-founders of another power metal band Helloween, which he was a part of from 1983 to 1989 and rejoined in 2016. He is a prominent figure in power metal and has sold millions of albums worldwide. He is regarded as "the godfather of power metal", having founded two seminal bands in the genre. In 2011, he joined the band Unisonic featuring former Helloween vocalist Michael Kiske. Hansen and Kiske reunited with Helloween in 2017 for a world tour with all current members, celebrating the 30-year anniversary of release of the albums Keeper of the Seven Keys Parts I and II.