One popular plot is that Arthur is initially shocked and angry when he discovers Merlin's magic, but then he gradually realizes how Merlin has been using it to protect him all along. For example, in some fanfictions, Merlin uses his magic to save Arthur from a seemingly impossible battle, and Arthur finally comes to terms with Merlin's powers and they become even closer friends, united in a new way to protect Camelot.
Another common plot involves Arthur struggling with his own beliefs. He's been taught that magic is evil, but now that it's Merlin, he has to re - evaluate. There are fanfictions where he goes on a journey of self - discovery, trying to find a way to reconcile his love for Merlin as a friend and his kingdom's stance on magic. He might consult with the court's wise men or even have secret meetings with Merlin to understand magic better.
Some fanfictions show Arthur becoming more dependent on Merlin's magic in certain situations. For instance, when facing a powerful enemy that can't be defeated by normal means. This changes the dynamic from just a king - servant relationship to more of a partnership. Merlin, on the other hand, might feel more confident in using his magic openly around Arthur, which also alters their interactions. They could have more equal conversations and decision - making processes.
It would likely become very strained. Arthur has been brought up to uphold his father's anti - magic stance. So, when Uther discovers Merlin's magic, Arthur might initially feel betrayed and distance himself from Merlin.
For Merlin, there are both good and bad consequences. On the bad side, some of the more traditional and anti - magic people in Camelot might try to oppose him. However, since Arthur now knows, he has a powerful ally. Arthur can protect Merlin from those who would do him harm. Also, Merlin can now be more open about using his magic for the good of Camelot, which is a positive change.
One interesting plotline could be Arthur's initial shock and then his gradual acceptance of Merlin's new identity. He might start to see Merlin in a whole new light and realize how much power Merlin truly holds.
In fanfiction, if Uther finds out Merlin has magic, it could lead to Merlin's immediate arrest. Uther is known for his extreme hatred of magic in the Merlin series. He might see Merlin as a great threat and try to execute him, just as he has done with other magic - users.
Arthur could also feel betrayed. He has trusted Merlin completely, and finding out about his magic might make him think that Merlin has been hiding something huge from him all this time. However, depending on how the fanfiction is written, he might eventually come to understand Merlin's reasons for secrecy.
One possible secret could be that Merlin is a powerful sorcerer from an ancient and powerful magical lineage. Maybe his family has a long - standing connection to Camelot that has been kept hidden.
I'm not sure about the most popular ones specifically. But you can start by looking on major fanfiction platforms like Archive of Our Own. There might be stories where the author takes a creative turn and has Arthur in a situation that seems like cheating on Merlin in their own fictional take on the relationship, often exploring complex emotions and consequences.
One popular 'Merlin Saves Arthur' fanfiction might be 'The Saving Grace' where Merlin uses his magic in a really creative way to rescue Arthur from a powerful dark sorcerer. It's full of action and shows the deep bond between them.
Some fanfictions focus on the theme of alternate universes. In these, the Merlin - Arthur kiss can happen in a completely different setting. For instance, they could be in a modern - day world where they meet in a different way than in the original story. Or perhaps they are in a world where magic is accepted openly, and their relationship develops more freely. This allows for creative interpretations of their relationship and the significance of their kiss.