Question

why magnet attracts only some metals why not other materials &metals

Answer 1

If you apply a magnetic field to an object, any magnetic atoms inside will respond to it and move to a new configuration, possibly causing a new magnetic field of their own, distinct from the field you're applying. If the permeability is a large number, it gets magnetized parallel to the external field, and there is attraction. If the permeability is small enough, it actually magnetizes opposite to the external field (diamagnetism) and is repelled; this is a very weak effect and can be observed with pure water.
In electromagnetism, permeability is the measure of the ability of a material to support the formation of a magnetic field within itself