Are you interested in a fun, metacognitive strategy for your students? Try this Ladder of Abstraction! Have students describe an object using as many adjectives as possible (without using the name), and then boil it down into the object itself. This comprises an object in the concrete sense. Afterwards, move up the "ladder" with abstract qualities. Ultimately, the goal is to have students "abstract" with both objects and vocabulary.
Thus, whereas a ladder is concretely "brown" and has "rungs," it is also a metaphor and made of matter. Try it for any object in the room. You may be surprised at your results!