Spinning an aluminum can in a motor stator - GIF

[desbromilow]

And Al has very little magnetic attraction?

Aluminium isn't magnetic, but the induced currents in the aluminium (because it is a conductor) create a magnetic feild which interacts with the rotating feild in the stator. Copper isn't magnetic either, yet moves in a magnetic feild when it has a current in it for the same reason (think coils in a loudspeaker). The forces exerted on a conductor (with current present) in a magnetic feild are defined by Lenz's law. Lenz's law has no consideration regardign if the conductor is a magnetic material or not since it is the current which is interacting, not the material containing the current.
The iron/steel in a commercial motor is predominantly there to help shape and concentrate the magnetic field... it also adds some other effects like rotational inertia, etc but the principal purpose is to shape the flux field to improve magnetic coupling, and therefore improve efficiency.