Question from class: *What do magnets interact with?*
Basically, everyone said “metals”. I am quite surprised. No one specifically indicated that magnets only interact with iron and steel (of the materials they would likely see). I understand that steel is a very common material they are likely to encounter, but what about aluminum? I think this points to the idea that very few of my students have actually played with magnets. This is a shame. Everyone loves magnets.
So, I propose you go out and give someone you love some magnets today.
Rhett Allain's Stuff 
I know what you mean, but magnets interact pretty strongly with any material, and particularly conductors. Try dropping a rare earth magnet through a section of copper tubing, for example. There’s a whole host of other examples, like ‘levitating’ aluminium blocks in MRI scanners … http://www.youtube.com/watch?v=fxC-AEC0ROk
I’m sure this wasn’t the idea in all – if any – of the student’s minds.
Magnets interact with aluminum. That interaction is why a speedometer works (or at least a classic, non-digital speedometer). A spinning magnet induces an eddy current in an aluminum cup.