A copper sheet can be hammered into a new shape without fracturing, while a sodium chloride crystal cleaves under the same treatment. Which feature of metallic bonding explains copper's behavior?

Core Concept

Metal cores sit in a pool of mobile, shared valence electrons whose bonding has no fixed orientation. When hammering displaces one plane of atoms relative to its neighbor, the electrons instantly redistribute and continue holding the shifted arrangement together, so the metal deforms instead of shattering. Nothing in this picture requires preserving a specific ion alignment, which is exactly what ionic lattices cannot survive.