What is the overall premise of the IDW Megatron comic series?

The IDW Megatron series focuses on the origins of Megatron, detailing his life on Cybertron before the Great War. It explores his initial ideals, his relationship with Optimus Prime (then Orion Pax), and the events that gradually led to his descent into tyranny and the formation of the Decepticons. It's a prequel to the main Transformers continuity established by IDW.