Brokeback mountain follows two men, who worked on a job in the Wyoming mountains together, fall in love, go their separate ways, and the complications in their lives. And, it is a story of an affair, that causes trouble.
Most of the movie follows Ellis Del Mar, who is engaged to his sweatheart Alma at the beginning of the movie. After Ellis and Jack Twist finish their summer job herding sheep on Brokeback Mountain, he gets married. And the movie skips through the next four years, as Ellis has two daughters, and Jack goes back to rodeoing in Texas. But, with two daughters, and not much money, Ellis' life and marriage become hard, and he never quite gets the hang of having a life that goes beyond being a ranch hand. And when Jack Twist comes by for a visit after four years, Ellis remembers that time on Brokeback mountain, and takes leave of his wife and kids for a few days. They end up doing this on and off for the next 15+ years. And along the way, Alma divorces Ellis, Jack's marriage becomes more distant and angry, and eventually, Jack is killed, and we are led to believe it was a hate crime.
Brokeback Mountain is a story of an affair. Ellis sees in Jack a relationship that is all happiness, in contrast to his marriage to Alma with all its responsibilities and troubles. And I think he realizes to a certain extant the mess he has gotten himself into. He repeatedly refuses Jack's entreaties to take the easy way out an run off with Jack, but the stress of dealing with Jack also seems to lead to him cutting of Alma and his kids emotionally. And the result is he with neither and both relationships are filled with conflict because he neither fully opens up to either, but defends each (Alma and Jack) against the other. Both Alma and Jack desire Ellis, but each only sees Ellis being loyal to the other. And Ellis either is angry, or completely passive, unable to resolve his conflict. And in the end, Ellis has nothing, all lost because he would not choose. Jack is dead, presumably killed when his homosexual side was seen by the wrong people. Alma has remarried, to someone what it seems that neither her or the daughters seem to have much respect for. Cassie (girlfriend) has left, and is confused and hurt because she has no idea why Ellis is so withdrawn despite her efforts. And all Ellis has is an unending series of small time ranch jobs, and no future ahead, or any desire for such.
What this does well is to show the costs of an affair. While Ellis is loyal in a way to the marriage, refusing to go run away with Jack even after the divorce, the affair resulted in Jack never being really there when he was with those who cared for him (wife, daughters, girlfriend). And his distractions with trying to manage them all don't work. And he knows his life is messed up.
Does the homosexual aspect of the story line matter? Actually, it works out well here. It creates another level of tension in a story about an affair, where there is that much more resistance to following your feelings and running away from responsibility. More reason for Ellis to stay in town with wife and daughters, that even the 'follow your heart' types can recognize. Having the other principle, Jack, who embodies the more 'act on your feelings' answer get violently killed was almost a distraction.
How is this as a movie? It somewhat suffers since its main character (Ellis) has as a personality quality the unwillingness to communicate (whether just his personality or also because he is hiding from everyone). Very intentionally, you do not know what he is thinking, only how everyone else responds to it and is affected by it. It requires the audience to fill in the holes (I believe the author of the short story this was based on did this intentionally) as I have. So it does turn into a 'it is whatever you make of it' movie. Compared to the Oscar winner of its year, Crash, it suffers from its unwillingness to say anything. Crash had lots to say, and much of it people dealing with contradictory messages about race. Brokeback Mountain is a story of an affair. A well done one. But not one that strikes me as one to remember down the ages.