What's the message? This is it..
The entire focus of the movie was on this one family. I suppose the rest of the world was in a mad panic. However, no one ever turns on a TV or goes online for "news" and we never get a glimpse. I suppose for the sake of keeping the budget, the movie couldn't diverge too much? I know Keifer's character wanted to keep the panic out of his family although the first part of the movie drove him mad, with his sister-in-law causing most of it, and even the impending DOOM of the planet didn't cause him to freak out, just calmly get up and take some pills and check out. I think the message is that even the end of the world can't be as bad as having to foot the bill for a doomed marriage! j/k!
However maybe THAT is the point? Justine was the "melancholia" in the first part. A disaster "waiting" to happen. Everyone knows it is coming, and it eventually does. Marriage over before it is even consummated. The "implosion" of her Melancholia is her screwing the young man on the golf course after blowing up at her boss. Second half, the actual planet is the disaster that is bound to happen. But Justine, becomes opposite of her first self, after going thru her own "melancholia" and found absolute peace while the others panic in their own way and can't get thru this "melancholia" and resort to falling apart. Two sides of the same coin. IMO, and I am no expert, but the message in this movie is, Expectations are what drive people to create melancholia. Doing what EVERYONE else wants you to do when none of it is what YOU want. It drives you MAD! The only one besides Justine that got it was her mother, when she simply said "run".
Brilliant movie.