It's similar to the metal core, except the part that switches polarities (comutator) is at the top. This is the coreless motor from a micro heli that i opened up.
It's like an outrunner. The permanent magnet is in the center, and the electomagnet is a very thin spinning cylinder made up of copper wires that slide in between the magnet and the steel wall. The part that switches polarities is in the lower right pic. Brushes are in the lower left. In a toy motor, there are three contact points, on the coreless, there are five.
On second thought, it's nothing like a metal core