One possible fanfiction could be that Merlin gets injured during a battle while trying to protect Arthur. Arthur then becomes extremely protective, refusing to let anyone else tend to Merlin's wounds. He stays by Merlin's side, worried sick, and vows to be more careful in the future to prevent Merlin from getting hurt again.
One common theme is loyalty tested. In many Merlin - Arthur hurt fanfictions, situations are created where Arthur's position as king or Merlin's role as his servant put their loyalty to each other on the line. Another theme could be sacrifice. For example, Merlin might have to sacrifice his magic or his safety to protect Arthur, or vice versa. Also, the theme of friendship in the face of danger is prevalent. They might be hurt physically or emotionally due to battles or political intrigue, but their friendship endures.
One common theme is loyalty. Arthur's protectiveness shows his loyalty to Merlin as his friend and servant. Another theme could be guilt. If Merlin is hurt because of Arthur in some way, Arthur feels guilty and that drives his protectiveness. For example, if Merlin takes an arrow meant for Arthur.
One well - received Merlin - Arthur hurt fanfiction is 'The Wounded King' which delves deep into Arthur's physical and emotional wounds after a major battle and how Merlin helps him through it. Another is 'Merlin's Sacrifice' where Merlin endures great pain to save Arthur from a dark spell. 'Arthur's Regret' is also good, it focuses on Arthur's regret after accidentally causing Merlin harm and his journey to make amends.
The banter between Merlin and Arthur in fanfiction is really interesting. It can range from light - hearted jabs at each other's habits. Merlin might poke fun at Arthur's love for jousting and how he always gets a bit too competitive. Arthur could retort by mentioning Merlin's clumsy attempts at serving him. Their banter also reflects the underlying respect they have for each other despite their different social standings. It's like a friendly sparring that keeps their relationship dynamic.
The 'Redemption' trope is also seen in some fanfictions. Maybe Arthur has made some mistakes in the past, and Merlin helps him to redeem himself. Or vice versa. It's a way to explore the characters' growth and development. And then there's the 'Battle Against Evil' trope where they fight side by side against dark forces, which really showcases their bond and loyalty.
I really like 'The Sword in the Stone' as a fanfiction - like take on Merlin and Arthur. It shows Merlin as this wise and mysterious figure guiding Arthur on his journey to become king. There are also some great interactions between the two characters that show the deep bond they share. You can find it in many libraries or online bookstores.
Merlin would likely be seen as a bit of an enigma at Hogwarts. His magic is different from the norm, so he might be a bit of an outsider at first. But his kind heart and loyalty would soon win over his classmates. Arthur would be the brave and headstrong character, perhaps a bit like a Gryffindor version of his usual self. He'd be eager to learn about combat magic and would probably be a natural leader in group projects or Quidditch teams.
During the time of Merlin's captivity, they could have long conversations that they never had before. Arthur might open up about his insecurities regarding magic and his kingdom, and Merlin could share his true feelings about serving Arthur. This would strengthen their bond in a new and unexpected way.
It could start with a slow realization of their feelings. Maybe they were friends for a long time and then suddenly, one day, they look at each other in a new light. After getting married, they become more protective of each other. Arthur might become more open to Merlin's magic, and Merlin would be more involved in Arthur's political decisions.