What makes some pure metals more ductile than other pure metals? I know ductility is defined as the ability of a material to be drawn into a wire, and one measurement of it is the percentage elongation from a tensile stress test. But does anyone know what is going on at an atomic level when the metal is being plastically deformed that makes some metals more ductile than others? Right now I think it might be the density of dislocations or other defects, but surely that can't account for such large variations in behaviours? Any help would be appreciated. EDIT: I removed the parentheses, but I'm sure I read somewhere that Aluminium is more... and by pure metals I mean not alloys.