What is the term for a metal's ability to be significantly deformed without rupture?

The term that describes a metal's ability to be significantly deformed without rupture is plasticity. Plasticity is a broad term referring to the capacity of a material to undergo permanent deformation when subjected to external forces. This deformation occurs without the material breaking or returning to its original shape, which is essential in processes like shaping metals through rolling, forging, or extrusion.

While ductility and malleability are often used interchangeably with plasticity, they have specific meanings within the context of deformation. Ductility refers specifically to a material's ability to be stretched into a wire, emphasizing tensile deformation, while malleability pertains to a material's capacity to deform under compressive stress, such as hammering into thin sheets. Both are forms of plasticity, but the term plasticity captures the overall ability to deform without fracture.

In this context, the broader term accurately encompasses the general concept of deformation in metals, making it the most appropriate choice.