Love and acceptance are quite common themes. Despite their differences, the male human and the female monster fall in love. This shows that love can transcend physical and cultural differences. And acceptance comes in as they both have to accept each other's flaws and differences to make the relationship work.
One common theme is the idea of the 'other'. The female monster represents something different from the human world, and the story often focuses on how the male human overcomes his initial fear or prejudice. Another theme is transformation. The relationship might cause the male human to change in some way, or the female monster to become more human - like.
One common theme could be the power dynamic. Since the female is an elite, there might be exploration of how the male human deals with her status and power. Another could be a kind of 'fish out of water' scenario if the male is from a more ordinary background.
One common theme could be adventure. The human male and female furry characters might go on an adventure together, facing various challenges. Another theme could be friendship that gradually develops into something more.
One common theme is the clash of cultures. Orcs and humans usually have different ways of life in fantasy settings.
Well, first of all, the theme of discovery is quite common. The male human and female Sangheili are likely to discover new things about each other's species, whether it's physical abilities, cultural norms, or ways of thinking. Then there's the theme of cooperation. In the fictional scenarios, they usually have to cooperate to face some kind of threat or achieve a common goal. And of course, there's the theme of attraction, which is the basis for their relationship in these fanfics. This can be both physical and emotional attraction, and how they navigate this in the context of their different species is an interesting aspect that many fanfics explore.
One common theme could be the overcoming of differences. Since an arachne is not human, there would be a lot of cultural and physical differences to work through. Another theme might be acceptance. The male human has to accept the arachne for who she is, with all her spider - like features. And of course, there's the theme of forbidden love, as such a relationship might not be considered normal in the setting of the story.
Often, the theme of discovery is present. The human discovers the alien's world and vice versa. It can also be about love against all odds. Their relationship might be frowned upon by their own species, but they still fight for their love. And there's also the theme of learning and growth as they adapt to each other.
One common theme could be the exploration of an unusual relationship in a science - fiction context. Maybe the idea of two very different species interacting in ways that are not typical.
A theme that frequently shows up is the protection of the weak. Toriel is a very motherly figure, and in these fanfics, she often extends that protectiveness to the male human. Also, there's the theme of cultural exchange. Since the human is from the surface world and Toriel from the Underground, they share their different ways of life. For example, the human might introduce Toriel to things like human music or art, while Toriel teaches the human about monster magic or the Underground's history. This exchange helps to strengthen their bond.
The exploration of power is also a theme. The male human may gain some unexpected power or have to deal with the power dynamics between the different factions. For example, he could be caught in the middle of the feud between the vampires and werewolves because of his unique position or abilities.