Starscream is the secondary antagonist of the 2007 film Transformers, Transformers: Revenge of the Fallen and Transformers: Dark of The Moon.
He is Megatron's second-in-command of the Decepticons and leader of the Decepticon Seekers. Outside of the films, it is shown that Starscream has a brutal tendency to usurp Megatron in the comics and whatever it takes.
Starscream is known for his treacherous nature; so he claims to be loyal to Megatron, he tries whatever he can do become the leader. When Megatron was killed by Sam Witwicky, Starscream wasted no time taking control at the leader. In the fifth film, as Megatron holds Starscream's severed head he refers to him as his "treacherous friend." He is also cowardly because according to Starscream's motto in Revenge of the Fallen to Megatron that cowards are the true survivors. He does this when he points out to Megatron that Optimus will defeat the Fallen