Ultimately, the movie's messages are about the importance of working hard and working together, being honest, and trying your hardest. Additional themes include humility, teamwork, and challenging gender stereotypes.
Mulan joins the Chinese army during wartime. She learns to fight with weapons. The Huns destroy Chinese villages and kill people (not shown). Some of the battle scenes are scary and intense. Tense sword battle at the climax. Explosions.
Some flirting. Shirtless male characters.
Mulan is a Disney Princess, whose brand reaches far and wide. Expect to see princess branding on consumer merchandise, food products, etc. as well as in books, websites, and other media.