Metals are malleable and ductile because they are made of hexagonal and cubic packed structures that can be moved by applying force to them. When force is applied, the atoms slide from one plane past atoms in a different plane.
The sliding of atoms when force is applied is the reason that metals can change their shapes. Since all things are made of atoms, including metal, the atoms must be moved in order to change the shape of the metal. Whether a metal is malleable, ductile or both, most metals are able to be changed with the use of force because their atoms are movable. In most, if not all metals, it is easier for the atoms to move when they are heated which is the reason that most metals are melted down or heated up before they are moved into a different shape.
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. Copper, nickel and tin are a few metals that are able to be pounded into thin sheets and able to be made into thin wires. When atoms move in different ways and can be pounded or stretched, they are both malleable and ductile.