One popular one is 'The Once and Future King' fanfic series. In this, Merlin often uses the term'sire' as he plays his role as Arthur's advisor. Another is 'Camelot's Heart' where the relationship between Merlin and Arthur is very much in line with the traditional Arthurian tales, and Merlin's use of'sire' is quite prominent.
In Merlin fanfiction, Merlin calls Arthur sire as a sign of respect. In the Arthurian legend and related fictional settings, sire is a term used to address a nobleman or a person of higher status. Merlin, being Arthur's servant and advisor in many versions, uses this term to show his loyalty and deference to Arthur's position as king or prince.
He might also get angry. Merlin has his own pride and after all he has done for Arthur, being insulted like this would make him furious. He could start yelling back at Arthur, listing all the times he has saved Arthur's life or the kingdom.
One possible reason could be a misunderstanding. Maybe Merlin did something that Arthur misinterpreted as betrayal or dishonesty. For example, if Merlin was secretly helping an enemy for a greater good that Arthur wasn't aware of at the time.
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.