Spider-Man has definitely been in the Avengers in the comics. His presence has added a fresh dynamic and his powers and wit have been valuable assets to the group.
One interesting storyline could be Spider - Man teaming up with the Avengers to fight a new super - villain that's a combination of different powers they've faced before. For example, a villain with the strength of the Hulk and the mind - control abilities of Loki.
Well, maybe he's got some secret mission that he doesn't want the Avengers to interfere with. You know, like protecting a particular person or some crucial information that he thinks the Avengers might mess up if they get involved.
Another possibility is that the Avengers are being manipulated by a villain. The bad guy could be using false information to make the Avengers believe that Spider - Man is a danger. So they go after him without really knowing the truth.
In a fanfic, Spider - Man could be injured while on a mission with the Avengers in outer space. Maybe they are exploring an alien planet and are attacked by some sort of bio - mechanical creatures. Spider - Man is separated from the group and gets severely injured by one of the creatures' acidic attacks. His injury makes it difficult for him to use his powers effectively, and the Avengers have to find a way to both get him back to Earth and find a cure for his injury.
The Avengers would be very concerned. Captain America would immediately take charge of the situation, trying to keep everyone calm while they assess Spider - Man's injuries. Iron Man would start scanning for the best way to treat him, using his high - tech equipment. Thor might offer some of his Asgardian knowledge of healing, if there was any. Black Widow and Hawkeye would be on guard, making sure there were no further threats while the team focused on Spider - Man.
In many Avengers fanfics, Spider - Man's sacrifice can be a very powerful plot point. It often shows his selfless nature. He might sacrifice himself to save his fellow Avengers or the world from a great threat. This kind of sacrifice also adds depth to his character as it shows his growth from a young hero to one who is willing to give everything for the greater good.