Starscream is a human, and the leader of the Seekers. He has a thirst for power and a flair for backstabbing his boss; Megatron to attempt to take the throne of General of the army he's in. Aside from that, he's an extremely intelligent and manipulative natural leader and veteran warrior, believing that the strength of one man over another is all that matters.  He can be ruthless and sadistic, but also doesn't take threats too seriously due to his hubris. Kind of silly at times.