Megatron, briefly known as Galvatron, is the main antagonist of the original continuity of Paramount Pictures‘ Transformers film series.
He is an extremely powerful, destructive, and warmongering Decepticon hell-bent on ruling over humankind and the Earth. His cause has led to him come in conflict with his former brother-in-arms and archenemy, Optimus Prime. Once a former student of Sentinel Prime, he appointed to be Cybertron's Protector and commander of it's Defense Force. However, Megatron resented Optimus, knowing he was a Prime and therefore Sentinel's favored student.
This anger allowed The Fallen to ensnare him and led to the revival of the Decepticons. Following the demise of both the Fallen and Sentinel Prime respectively, Megatron was brought back to life thanks to the machinations of Cemetery Wind, KSI, and Lockdown, and eventually teamed up with Quintessa to revitalize Cybertron by destroying the Earth after learning that the planet is in fact Unicron.
In the first three films, he was voiced by Hugo Weaving.