Oooooh, you have to see this movie. It's the most beautiful movie I've seen in a long time. The cinematography is amaaaazing. Melancholia had me entranced from the beginning.
Two major things are happening here: Justine's (Kirsten Dunst) marriage is falling apart, and she has a difficult relationship with her sister, Claire (Charlotte Gainsbourg). AND there's a newly discovered planet that's been hiding behind the moon, and it's hurtling toward the earth, about to end life as we know it. The film is in two parts: The first shows Justine's wedding and her breakdown during the reception. There's little mention of the planet. The second part focuses on Justine's relationship with Claire and the former's mental recovery. And the Impending Doom.
That summary does not do justice to this movie. Remember, I'm a book person (and I checked: sadly, Melancholia isn't based on a book). It's a visual experience (speaking of visual, I'll warn you that there's some tasteful nudity). While the acting is superb, the cinematography outshines it. And the end! I was sobbing at the end! Really, it's soooo good.