One popular theme is the relationship between Merlin and Arthur. It could be romantic, platonic, or exploring their friendship in different scenarios. Another theme is Merlin's magic and how he hides it or uses it in different ways.
You can try fanfiction websites like Archive of Our Own (AO3). It has a vast collection of Merlin fanfictions. Just use the search function and type in 'Merlin' to browse through various stories.
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.
One popular theme is unrequited love. Arthur might want Merlin but be unable to express it due to his status or other obligations. Another theme could be the discovery of Merlin's magic and how that affects Arthur's feelings towards him.
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.
One common theme could be loyalty. Merlin, being a soldier, would show loyalty to his comrades, his cause, or his kingdom. Another theme might be sacrifice. Soldiers often have to make sacrifices, and in a Merlin - as - a - soldier fanfiction, he might sacrifice his personal desires for the greater good. Also, the theme of honor could be prominent. He would strive to uphold his honor in battle and in his interactions with others.
Some Emrys Merlin fanfictions are centered around Merlin's true identity as Emrys being revealed earlier than in the show. This can lead to all sorts of new plotlines, such as how the characters would react to his power and prophecy. Others might be about Merlin using his Emrys powers to save Camelot from greater threats that were not in the original series. And then there are fanfictions that are more about the emotional journey of Merlin as Emrys, dealing with the loneliness and the great burden that comes with his powers.
One reason is that it allows for a lot of character development. When Merlin dies, other characters have to step up and change. For example, Arthur might have to become more self - reliant in a 'Merlin Dies' fanfic. Also, it can explore darker themes like grief, loss, and the struggle to move on, which many readers find fascinating. Moreover, it can be a way to explore 'what if' scenarios that the original show didn't cover.
Sure, there are popular ones. A lot of it has to do with the fact that this concept goes against the grain of the original story. Fans are always interested in seeing different angles. Some of these fanfictions become popular because they build on the existing lore in creative ways. For example, they might show Merlin protecting Mordred from other magical threats or political intrigues within Camelot. The character development in these stories, especially how Mordred responds to Merlin's protection, can also be a big draw for readers.
A common theme is also the way the other characters in Camelot discover or adapt to Merlin's muteness. Some stories might focus on how Gwen, for instance, tries to help Merlin communicate or how the knights interact with him. There could also be themes related to Merlin's hidden powers being even more mysterious because of his inability to speak and explain them.
Another theme is Merlin's magic and how he hides it or uses it to save the day. There are also fanfictions that focus on Merlin's backstory, like his life before coming to Camelot and his family.