In my experience as a technical instructor -- who frequently has to introduce concepts like the HTML DOM to students who have a hard enough time with markup --

In my experience as a technical instructor -- who frequently has to introduce concepts like the HTML DOM to students who have a hard enough time with markup -- overly simplified metaphors can get over the "can't learn, too hard!" barrier that adults tend to put up when they're expected to learn something new. FWIW, I use the car metaphor, and as a class, we all break it down into simplified properties, methods and events.