Basically Loki, who's on earth, finds out that in order to stay, he has to marry to someone from Earth. He then goes through the Avengers before settling on one of them and tricking him (I distinctly remember it being slash) into marrying him. I vaguely remember there's a scene where Odin sends his little golden soldiers down to try to take him back because he did something wrong and his new husband was like OH HELL NO.
Thanks in advance!!