They could end up having a friendly competition. The Avengers with their superpowers on Earth and the Guardians with their space - faring skills. Iron Man might be intrigued by Rocket's weapon - making abilities and try to collaborate on some new tech. And Thor could find common ground with Drax in terms of their brute strength and warrior spirit.
Hulk might not care much about the Guardians' antics at first. But if they accidentally made him angry, things could get really wild. Thor, on the other hand, would likely be more open - minded. He's already used to dealing with different realms and species, so the Guardians' oddities might seem normal to him compared to some of the things he's seen in Asgard.
A 'Guardians of the Galaxy meet Avengers' fanfiction might involve a lot of character interactions. Drax could be fascinated by the Hulk's strength and constantly challenge him to tests of might. Gamora and Black Widow could share their combat experiences and train together. Also, Groot and Thor might have an interesting exchange. Thor could be amused by Groot's simple yet endearing nature while Groot might be intrigued by Thor's lightning powers.
Star - Lord is also very popular. His roguish charm and his connection to the cosmic side of the Marvel universe bring a unique flavor to the fanfiction. Writers love to explore his backstory more deeply and his potential relationships with other characters.
Another cool fanfiction idea could be a time - travel story. The Avengers accidentally send themselves to the time when the Guardians were just forming. This leads to a chaotic but interesting adventure where they have to work together without ruining the future of both groups.
One interesting fanfiction could be about a team - up mission between the Avengers and the Guardians. Maybe they have to face a new, powerful cosmic threat that neither group could handle alone. For example, a super - villain who can control dark matter and is using it to destroy planets on a whim.
Black Widow is another popular character. Her skills as a spy and fighter make her a great addition to any crossover fanfiction. She could be involved in a mission with the Guardians where she has to use her stealth and intelligence to outwit their enemies. Also, her complex backstory gives writers a lot to work with when creating new storylines.
One interesting fanfiction could be about the Guardians and Avengers teaming up to face a new, powerful villain from another dimension. In this story, the different personalities, like Star - Lord's charm and Captain America's leadership, would clash and then blend as they figure out how to defeat the enemy.
One popular storyline is about the backstories of the characters. For example, stories that explore Rocket's past as an experiment are quite common. Another is the relationships between the Guardians, like the budding romance between Star - Lord and Gamora. There are also many fanfictions that deal with the Guardians facing new threats that are not in the movies, such as ancient cosmic entities.
The best place to find 'Guardians of the Galaxy' fanfiction is probably AO3. It has a really well - organized system. You can search by rating, word count, and most importantly, by the type of story you want, like adventure - filled ones or character - centric ones. FanFiction.net also has a wide range of stories. But be aware that the quality can vary a lot more on that site compared to AO3.