One popular theme is the forbidden love aspect. Since archangels are often depicted as powerful and otherworldly beings, a relationship with a human soulmate can be seen as forbidden. Another theme is the idea of the soulmate bond being able to overcome great obstacles, like the battles and power struggles in the Supernatural universe.
The concept of redemption through love is also quite common. An archangel might be on a path of destruction or darkness, but the connection with their soulmate can lead them to redemption. Also, the theme of sacrifice is popular. The soulmate may be willing to sacrifice themselves to save the archangel or vice versa in many of these fanfictions. This adds a lot of drama and emotional depth to the stories.
Another theme is the exploration of different realms. As Gabriel has the ability to travel between realms, fanfictions often take the soulmate on adventures through different planes of existence. This allows for some really creative and exciting storylines, with the couple facing various challenges in different supernatural settings.
One popular theme is the sister's relationship with her archangel brothers. It could be about her trying to fit into their world or dealing with their overprotectiveness. Another theme is her own powers and how she discovers and controls them in the context of the Supernatural universe.
A lot of fanfictions focus on the idea of Castiel being different from other angels because of his connection to the Winchesters. There are themes of forbidden love, like a romantic relationship between Castiel and an archangel which goes against the angelic rules. Also, the exploration of Castiel's true purpose and how it relates to the archangels' plans is a big theme.
Redemption is also a common theme. Given his complex backstory in the show, fanfictions often delve into Gabriel's journey towards redemption. This could involve him making amends for past actions or finding a way to atone for his mistakes. Writers might explore his relationships with other characters like Castiel or the Winchesters in the context of this redemption arc. It can be really interesting to see how different authors interpret his path to redemption.
One common theme is the origin story of the 5th Archangel. Writers often explore how this archangel came to be in the Supernatural universe. Another theme is its relationship with the other well - known archangels like Michael and Lucifer.
You can try websites like Archive of Our Own (AO3). It has a vast collection of fanfiction in various genres, including those related to supernatural archangels and soulmates. Another option is Fanfiction.net, which also hosts a large number of such stories.
The power dynamics between different supernatural species is also a big theme. For example, if a werewolf and a vampire are soulmates, how do their natural instincts and powers interact? It can lead to some really interesting plot twists. In addition, themes of sacrifice and protection are common. Soulmates will often go to great lengths to protect each other, even if it means sacrificing their own power or status in the supernatural hierarchy. And this can create a lot of emotional and action - packed scenes in the fanfiction.
Fate is also a big theme. Fanfictions often play with the idea that the characters were always meant to be together as soulmates, no matter what they've been through. It gives a sense of destiny to their relationships, which adds a whole new layer of depth to the characters' stories in the Supernatural context.
One common theme is power and its consequences. Female archangels often have great power, and the fanfictions usually explore how they handle it, whether they use it for good or are tempted by the dark side of that power.
One common theme is the struggle between Mikael's dark nature and the concept of a soulmate. Since he is often portrayed as a rather menacing character in 'Supernatural', the fanfictions might explore how he deals with the idea of having a soulmate who could potentially change him.