Why are metals malleable whereas non-metals are not?

It all depends on the deformability of the material on a microstructural scale. Martensitic steels are brittle, because the crystal structure cannot accommodate serious deformation, but if you temper the same steel the change in crystal structure allows it to deform and be malleable. read more

Most metals are malleable because the atoms can roll over each other and retain the structure of the crystal.Metallic bonds involve all of the metal atoms in a piece of metal sharing all of their valence electrons with delocalized bonds. read more

Most metals are both malleable and ductile, but malleable and ductile are two different things. Ductile metals are able to be pounded down into a smaller, thinner sheet of metal. Malleable metals, like copper and nickel, are able to be stretched out into thin wires. read more