why always electric charge resides on the surface

charge always resides on the surface of a CONDUCTOR because the electric field throughout the interior of the surface must be identically zero.

Dear friend charge is basically due to the presence of opposite charge in surrounding of that charged particalor near that partical.as the electric field of the charged produced come incontect with the metal surface and it leads to polarity and due to the formation of a series of charge on the surface of metal body it also produce field and then field of the the first partical is now reppled by the new field and so we can say that charge do nor reside inside the metal body.

if you have any doubt regarding about this plz do informe me...