The main character, Peter Quill, lost his mother to cancer at a young age. Soon after his mother died, Peter was suddenly abducted by an alien ship for no apparent reason, other than a lot of plot convenience. This gives all the makings of a normal superhero movie: dead parent, aliens and some kind of weird transport.
After he grows up Quill becomes kind of a thief and gets arrested. He teams up with Gamora, a blue female assassin, a raccoon called Rocket, a walking tree called Groot and Drax, who looks like a wrestler with tattoos all over his body. They all want to destroy Ronan, an evil alien bent on destroying the galaxy with an infinity stone they’re trying to sell. Like the cube in The Avengers, the infinity stone has a whole movie built around people trying to keep this object from falling into the wrong hands.
After fighting, breaking out of jail, almost dying and meeting some weird collector, the group finally gets to fight the main villain.