A tragic movie depicting the relationship between Sid Vicious (of The Sex Pistols fame) and Nancy Spungeon. While Sid and Nancy both die, the movie shows a point of view not commonly taken by most people. This is that Sid is the protagonist and Nancy is the antagonist. The conflict is Sid trying to overcome Nancy, and not Nancy trying not to get stabbed by Sid.
To explain this movie I am going to relate it to "Death of Salesman" written by Arthur Miller. The characters in Sid and Nancy and Death of a Salesman can be misinterpreted. Willy Loman is a character who puts his hope and ambition into the American Dream. Unfortunately in the end he decides his life is not worth anything more than the amount of his life insurance policy. Willy Loman has many quirks and is constantly on emotional ups and downs. The major question in Death of a Salesman is whether Willy is actually a tragic hero. Most people will opt to say that Willy is indeed a tragic character and despite his flaws he is a tragic hero.
Likewise to understand Sid and Nancy you must put some of Sid's character flaws aside. Throughout the movie Sid is trying to pull himself out of the rut he is in. Every time he starts to get somewhere, Nancy pulls him back down. Throughout the movie Sid is sympathetic to those that are weaker. There is the scene where some kids are bullying another kid Sid helps the underdog. There are several scenes where Sid shows some grasp on reality, but Nancy drags him back in.
To be able to enjoy the movie, you must realize Sid is flawed. (This is a MAJOR understatement.) Though through his flaws, he is constantly trying. The character must have done something right considering his success with the cover of My Way. While he never completely overcomes his flaws, I wished that he would. Each time he was thrown down I hoped he would be picked up.