Something apt is perfectly appropriate, clever and well-suited to the matter at hand. A "Cinderella story" might be an apt metaphor for an underdog team that makes it to the championships.
The wee cousin of aptitude, apt has the same root meaning of strength and ideal appropriateness. It can also be used in the form "to be apt to" meaning "to be likely to" do something: "With his dark, brooding persona, actor Christian Bale is an apt Batman, and audiences are apt to come to the theatres in droves to see him fight villains."
