Dear Arun, Magnets influence the magnetic field of iron in such a way that the magnets do attract to iron. Before an iron piece  enters the magnetic field of a magnet, the polaraization of atoms in the iron are random. But once the iron is exposed to the  magnetid field, the electrons position themselves in alignment with that of the magnetic field. This creates an attraction between the 2 objects.

Hello there!

Greetings !

It's not like magnet attracts only  iron,  it attracts other materials like nickel,  cobalt etc it is due to the influence of its magnetic field upon the iron etc that these materials get attracted.  When exposed to the magnetic field, the atoms begin to align their electrons with the flow of the magnetic field, which makes the iron , nickel etc magnetized as well. This, in turn, creates an attraction between the two magnetized objects and thus magnet is able to attract iron , nickel etc.

Thankyou