What property of metals allows a jeweler to hammer a piece of silver to make jewelry?
Malleability describes the ability of some materials to be hammered or otherwise forced into a different shape, without breaking. Most metals are highly malleable.
The reason for this is due to the nature of metallic bonding. Bonds between atoms in a metal are non-directional. Their strength doesn't depend on how the atoms are arranged.
Compare this to the bonds in an ionic lattice, where two or more types of ion are arranged in a rigid 3D structure. Any change to the shape of the lattice weakens those bonds and can cause the whole structure to break.