I show you my square knot. I untie it and tie it slowly while you watch. Then you try to tie a knot like mine. We use models in teaching because they work. Models let people know what we want.
People are models themselves.
A girl models a dress for a customer. A leader is a model whether he wants to be or not. He doesn't have to tell the group to follow his example. In fact, he can even tell them not to follow his example, but they will. Setting an example is more than staying out of trouble.