Materials are classified based on their response to a magnetic field as Ferromagnetic, Paramagnetic and Diamagnetic materials.
Ferromagnetic materials are materials which have a large susceptibility to magnetic fields. These materials can get magnetised when placed in an external magnetic field. They experience strong attraction to magnetic fields. This behaviour comes from the large magnetic domains in these materials. In the demagnetized condition, these domains are aligned in different directions. However, when they are placed in a magnetic field, these domains get aligned in the same direction. Thus, the material as a whole is magnetized.
Examples of Ferromagnetic materials are iron, cobalt and nickel.
Paramagnetic materials experience a weak attraction to magnetic fields. This magnetic field comes from the magnetic moments of unpaired electrons in the materials. There are no domains in paramagnetic materials. Examples of paramagnetic materials are magnesium, lithium and tantalum.
These materials have negative susceptibility. These materials are slightly repelled by magnetic field. There are no unpaired electrons in these materials. All the electrons have paired and hence the magnetic moment of these electrons cancel each other. Copper, Gold and Silver are examples of diamagnetic materials.