Why can metals bend substantially before breaking?

Metals can bend substantially before breaking because of their unique atomic structure and the nature of the metallic bond. Unlike materials with rigid, directional bonds, metals consist of positive ions surrounded by a "sea" of nonlocalized valence electrons that move freely throughout the crystal lattice.1

This nondirectional binding force allows the atoms to slide past one another without fracturing the material. Because the valence electrons act as a buffer between the positively charged ions, they prevent the ions from repelling each other when they are displaced during deformation.1

This capacity for plasticity is further facilitated by the simple, close-packed arrangement of atoms in metallic crystals. When a metal is stressed, it undergoes plastic deformation through the movement of structural defects known as dislocations along specific slip planes. While these dislocations allow the metal to change shape, continued deformation eventually causes them to intersect and form tangles, which creates obstacles to further movement and increases the metal's hardness—a process known as work hardening.2341