Well, clearly Damon and Bella are the main characters. Damon, who might bring his complex vampire nature, his charm, and his sometimes dark past. Bella, on the other hand, could be portrayed with her own unique qualities, perhaps her strong will and her ability to adapt to the supernatural world she enters through her mating with Damon.
One common theme is the struggle against external forces. In many of these fanfictions, there are other characters or situations that try to come between Bella and Damon. Another theme is the discovery of self through the relationship. Bella may find new aspects of herself because of her connection with Damon. And, of course, there's the theme of destiny. That they were meant to be mates is a central idea in most of these stories.
One interesting plot could be Damon and Bella having to face a powerful supernatural enemy together. They combine their unique powers and skills to protect their relationship and the people they care about.
You can start by looking on fanfiction.net. It has a vast collection of fanfiction stories, including those related to 'bella and damon mates'. Just use the search bar and type in the relevant keywords, and you'll likely find a bunch of interesting reads.
There's also 'Bella and Damon: A New Chapter'. In this fanfiction, it takes a different approach by placing them in a modern urban setting. The story focuses on how they navigate their newfound mate status while dealing with the challenges of normal life, like jobs and social circles. It's a fresh take on the concept.
One common theme is the clash of different vampire lore. Bella is from a world where vampires are more like 'gentle' predators in a way, while Damon is from a more 'edgy' and dangerous vampire world. So, exploring how these two concepts mix is a big theme.
One popular 'bella and damon are mates fanfiction' is 'The Unlikely Bond'. It explores their relationship in a unique way, with lots of emotional depth. Another is 'Mates Against All Odds' which has great plot twists.
One great fanfiction I know is 'The Unlikely Bond'. It really delves into how Bella Swan and Damon Salvatore could form a unique connection in a world where their two different story universes collide. The author does an amazing job of portraying their characters and how they interact with each other.
Damon could be a vampire or some other powerful supernatural being. Bella might be a human, perhaps with some special quality that makes her a target for James. Maybe she has a unique scent or power that she's not even aware of yet.