In fanfiction, if the Avengers go to Asgard, there could be a big clash at first. The Asgardians are proud warriors and the Avengers have their own ways. But then they might team up to face a common threat. For example, a powerful dark magic user could be targeting both Earth and Asgard. The Avengers with their diverse skills and the Asgardians with their magic and strength could form an unbeatable alliance.
Probably Heimdall. He guards the Bifrost, the Rainbow Bridge that leads to Asgard. He has the ability to see all, so he'd be the first to spot the Avengers coming. And he's not one to let just anyone pass without a bit of interrogation.
One reason could be that they see Loki as a victim of circumstances. Maybe they've come to understand that his actions were often influenced by forces beyond his control, like Thanos' manipulations. So they decide to defend him in Asgard.
A common plotline is the Asgardian princess sister coming to Earth to seek help from the Avengers. Maybe Asgard is under some sort of threat, like a new powerful enemy has emerged, and she believes the Avengers can assist. Another plotline could be her being exiled from Asgard and finding a new home and purpose with the Avengers.
You can start by looking on fanfiction websites like Archive of Our Own (AO3) or FanFiction.net. These platforms have a vast collection of Avengers fanfiction that might involve Asgard. Just use the search function on the site and type in relevant keywords like 'Asgard' and 'Avengers' to narrow down your results.
Maybe Loki is wrongly accused of a crime in Asgard. The Avengers, having had their own experiences with false accusations, step in to defend him. They believe in justice and know that Loki might not be guilty.
One popular theme is the interaction between the Asgardian characters and the Avengers. For example, Thor introducing his Asgardian culture to the Avengers team members. This can lead to interesting scenarios of cultural clash and cooperation.
One popular type of fanfiction in this category might involve the sister of Thor or Loki, who is a princess of Asgard, interacting with the Avengers. For example, she could be a powerful magic - user and help the Avengers in their battles against new threats. There are many fanfiction platforms like Archive of Our Own where you can search for such stories using relevant tags like 'Asgard princess' and 'Avengers' to find some great reads.
If the Avengers go to the future in fanfiction, it would be a wild ride. They could find that the Earth has been taken over by an alien race that they've never seen before. Their powers might not be as effective as they are in the present. They would have to adapt quickly, learn about the new political and social structures in the future, and find a way to either prevent this future from happening if it's a bad one, or ensure that it comes to pass if it's a good one. They might also have to deal with time paradoxes, like if they change something in the future, it could have a ripple effect on their present.
In a fanfiction where the Avengers go to Hogwarts, there would be a clash of cultures. The Avengers are used to a world of high - tech and superpowers based on science, while Hogwarts is all about magic. Iron Man would likely be skeptical of magic at first, but as he sees the power it holds, he might start to think of ways to integrate it with his technology. The students at Hogwarts would be in awe of the Avengers, and the Avengers would have to learn to respect the magical world's traditions.