"Melancholia" is an art film by controversial director Lars von Trier. While most of his movies are extremely violent (often sexually), this movie is actually quite calm, even though it deals with the possible end of the world. In fact, this movie is depressing and has not a single happy moment. On the other hand, it is not any disturbing or action-ish, leaving enough space for the beautiful visuals and dialogues. This movie is NOT for lovers of mainstream movies. Starting with extreme slow motion scenes, it soon changes into a dramedy about a wedding that ended as a disaster, only to change again, this time into a mature end-of-the-world drama. If you love art or off-beat movies, then you should watch this original, unusual movie. If you like Hollywood blockbusters only, then don't. Overall, it is very original and beautifully filmed, and I recommend it.
As for the age restriction, i don't know what the fuss is about? There is one scene of non-sexual nudity (we see breasts, but no genitalia) and one not too graphic sex scene (it is clear what's going on but we don't see much because it is shown from a distance).
It is okay for mature teens.