I am Legend is the story about a survivor of a plague that turned virtually all of the world into vampiric monsters of the night. The hero is a doctor who struggles to reverse the condition. I was pleasantly surprised at this movie. I like post apocalyptic movies and this one delivers. Unlike many post-ap movies, the hero, Robert Neville (played by Will smith), is a real and virtuous hero. Aside from the great action and story, there is a solid moral backbone to the story. God is portrayed as real and as acting with good purpose, even when great destruction comes. There is a prayer that sounds similar to something an evangelical would say and it is portrayed in a positive light. The movie is in no way "preachy" (not that this is bad) and positive religious themes are present but subtle. And again, while subtle, the God of the movie is the Christian God. It takes a bit of observation to catch this, though. The movie also presents heroism and self-sacrifice as positive virtues. The movie differs quite a bit from the darker book. I won't spoil things by explaining how. But if you have read the book, expect only a loose connection. I actually like the movie much more than the book. The PG-13 rating comes from "intense sci-fi action and violence." The violence is not over the top and is to be expected in this kind of movie.