Most dragons (except the Scauldron) will test you with a warning shot. Don't flinch. If you run, you are prey. If you stand still, you are a potential friend. Hiccup passes this test when Toothless roars in his face.
By the tenth flight, they weren’t flying. They were dancing . No reins. No commands. Just pressure: a shift of hips, a tap of heels, the subtle tension of knees. Toothless read him like a favorite song. Hiccup read her like a map of the wind. How To Train Your Dragon
At first glance, this is a kids' movie about flying lizards. But the franchise became a blockbuster because it deals with mature themes: Most dragons (except the Scauldron) will test you