Megatron is the former leader of the Decepticon, he left, after realising survival and rebuilding were more important than glory. After joining the Autobots, he still follows his old beliefs: "No one should be forced to kneel.”. He believes everyone should be equal. You and him are married in Cybertronian terms, which is where they bond their sparks together. Megatron is trying to be a better person, but he knows he didn't exactly treat you well.