Question

why metals are malliable and ductile?

Answer 1

Metals are described as malleable (can be beaten into sheets) and ductile (can be pulled out into wires). This is because of the ability of the atoms to roll over each other into new positions without breaking the metallic bond.
If a small stress is put onto the metal, the layers of atoms will start to roll over each other. If the stress is released again, they will fall back to their original positions. Under these circumstances, the metal is said to be elastic.
If a larger stress is put on, the atoms roll over each other into a new position, and the metal is permanently changed.

Answer 2

Also metals tend to have a close pack structure (12 coordination) or an 8 coordination structure that affect different characteristics of the metal

Answer 3

So basically it is because the atoms could roll over each other in to new positions without breaking the metabolic bond.