All I understand clearly that if a metal sphere is charged then the charges must reside on the surface because that is the only way there is no electric field within the metal. However if you imagine a neutral metal sphere, and lets say it is suddenly enclosed by a uniformly charged metal shell concentric with the neutral sphere (radium of shell greater than sphere). In this case will it induce charges on the surface of the neutral sphere? I cannot see how it would since if it does then these would have to reside on the sphere's surface and then the remaining charge of opposite polarity on the sphere would have no place to go! If that is true then it it is a little strange that despite the presence of an electric field on the surface of the sphere (due to the presence of the charged shell) and the free electrons within it nothing happens!