Annie Dillards essay "Living Like Weasels" is a great for teaching analogy.

I assign the students to read it for class.

Then in class I break them up into groups and give each group a paragraph.

Each paragraph is full of small analogies or metaphors, but all of these support Dillard's over all analogy which is that living like a weasel is like living well/to our full potential.

Sample paragraph

Our look was as if two lovers, or deadly enemits, met unexpectedly on an overgrown path when each had been thinking os something else: a clearing blow to the gt. It was also a bright blow to the brain, or a sudden beating of brains, with all the charge and intimate grate of rubbed balloons. It emptied our lungs. It felled the forest, moved the fields, and drained the pond; the world dismantled and tumbled into that black hole of eyes. If you and I looked at each other that way, our skulls would split and drop to our shoulders. Be we don't.

After piecing out all of the smaller analogies, I have the students start working on the larger one.

I introduce them to the idea of the vehicle and the tenor (or source and target), and then we decide what is the vehicle and tenor of this essay. This works for showing them that the vehicle (in this case the weasel) is not really the point of an analogy essay; it is just a means to get us to better understand the tenor.