Diamagnetic substances are materials that exhibit a weak repulsion to magnetic fields. This occurs because their electrons are paired, which means that their magnetic moments cancel each other out. When exposed to a magnetic field, these substances create an opposing magnetic field, resulting in a slight repulsive effect. Common examples of diamagnetic materials include copper, bismuth, and gold. Unlike ferromagnetic or paramagnetic materials, which are attracted to magnetic fields, diamagnetic substances do not retain any magnetization once the external field is removed. This property makes them useful in various applications, such as in magnetic levitation and magnetic resonance imaging (MRI).