There are multiple artists with this name:
1) Mantas is a death metal band from Orlando, USA. They formed in 1983 and changed their name to Death in 1984.
2) Mantas is a heavy metal/ industrial death metal band from UK. Mantas is the guitarrist of the Britsh Black Metal band Venom .
3) Mantas is a blackened thrash metal band from California, USA.
4) Mantas is a Lithuanian singer and actor.