One idea could be a human mechanic who discovers Megatron in a damaged state and tries to repair him while hiding him from other humans and Autobots. This could lead to a complex relationship where Megatron starts to question his views on humans.
A plot could involve a human scientist who is kidnapped by Megatron to help him with some advanced technology. But during their time together, the human gradually shows Megatron the value of life and friendship, which might change his evil ways. There could be many challenges and conflicts as the Autobots try to rescue the human and stop Megatron's plans at the same time.
Perhaps a story where a young human gets lost in a world full of Transformers and is found by Megatron. Instead of harming the child, Megatron sees an opportunity to use the human as a bargaining chip. However, as time passes, he becomes protective of the child, which puzzles his Decepticon comrades and creates a rift within the Decepticon ranks.
One idea could be a story where a human mechanic is the only one who can understand Megatron's complex machinery, and they form an unlikely bond. Another could be a post - war scenario where a human diplomat tries to negotiate with Megatron for peace, leading to a deeper understanding between their species. Maybe a human scientist discovers a way to communicate with Megatron on a mental level, and they end up sharing knowledge that could change both of their worlds.
One idea could be exploring how the other Transformers react to Megatron in this unexpected state. Maybe some are shocked, while others see it as a chance for a new beginning in the ongoing conflict.
One interesting plot could be Beast Wars Megatron getting his hands on a powerful ancient artifact on Earth that gives him an edge over the Maximals. This could lead to a series of battles where the Maximals have to figure out how to counter this new power. Another idea is a fanfiction where Megatron forms an unlikely alliance with a small group of Maximals to face a greater threat from a third, previously unknown faction. This would be full of tension as they try to work together while still being enemies at heart.
Well, a plot idea could be that there is a prophecy about Bumblebee and Megatron. It says that they will either bring about the end of the Cybertronian race or save it. This forces them to interact more and try to figure out what the prophecy means. Another interesting plot could be that Megatron's mind is somehow transferred into Bumblebee's body and vice versa. They have to live in each other's shoes for a while and this changes their views of each other. And then there could be a plot where a new technology is discovered that can end the war, but Bumblebee and Megatron have different ideas on how to use it, leading to a complex relationship and many conflicts.
One idea could be a crossover where Megatron somehow ends up in the RWBY universe. He might see the potential for power in the Dust and try to take control of it. Another idea is that the RWBY characters have to team up with an Autobot to stop Megatron from causing chaos in their world.
Another plotline could involve Megatron using his knowledge from being a Transformer in his new human form. Maybe he uses his strategic skills to solve human problems, like helping in a corporate takeover in a more ethical way than the humans were planning.
Perhaps a fanfiction where a powerful artifact is discovered that has the potential to change the balance of power on Cybertron. Megatron wants it for his own gain, and Optimus Prime wants to protect it. But when they both touch it simultaneously, they are transported to an alternate dimension where they must work together to find a way back, all while learning more about each other than they ever thought possible.
There could be a fanfiction where a strange energy source affects Optimus Prime and Megatron, causing them to swap personalities or abilities. This would be a humorous yet also thought - provoking plot. They would have to navigate their new selves while still trying to lead their factions. The Autobots would be confused by an aggressive Optimus and the Decepticons would be equally bewildered by a more pacifist Megatron.
One idea could be an OC who is a medic that gets captured by Megatron. Megatron initially sees the OC as a tool to use against the Autobots but gradually develops an odd respect for the OC's skills and tenacity. Another plot could involve an OC who has a special power that Megatron wants to harness for his own evil plans. As he tries to manipulate the OC, the OC starts to see through his lies and tries to turn the tables on him. A third plot might be an OC from a different dimension who accidentally lands in the Transformers Prime universe and catches Megatron's attention. He's intrigued by this strange new being and tries to either recruit or destroy the OC.
Perhaps a fanfiction where Soundwave gets damaged in a fight and Megatron has to make a difficult decision about whether to risk everything to save him. It could explore their loyalty to each other. Or a plot where they are betrayed by one of their own and they have to work together to expose the traitor.