They describe themselves as "melodic power metal", I'd be more inclined to say "neo-classical progressive metal", but genres and labels are rarely accurate when applied to music.
Anyway, the bottom line is that Kamelot are an excellent, high quality metal band who include lots of orchestration and keyboards in their work.
Every album since "The Fourth Legacy" in 2000 has been brilliant, with their latest effort "Epica" being the brilliantest of all. If you like great melodic metal and album covers featuring beautiful girls then Kamelot are the band for you.
Kamelot - Official Website