Magnets not only attract iron, but also B-group transition metals such as cobalt and nickel, as well as various alloys, compounds, and the like. It should be emphasized that all materials are magnetic. Generally, magnetics are divided into five types: paramagnetic, antimagnetic (all materials are diamagnetic), ferromagnetic, antiferromagnetic, and ferrimagnetic. Objects with ferromagnetic and ferrimagnetic properties are what we often call objects that can be attracted by magnets because they have a large response to the external magnetic field and produce a large force. The other three are actually responding in the field, but the order of magnitude is too low, and macroscopic measurements are difficult to find.