Metallic Bonds:

Another chemical bonding mechanism is the metallic bond.  Within the metallic bond, an atom achieves a more stable configuration through sharing the electrons in its outer shell with several other atoms. Metallic bonds prevail in elements in that the valence electrons are not strongly bound along with the nucleus, namely metals, therefore the name metallic bonding.  Within this kind of bond, every atom in a metal crystal contributes all the electrons in its valence shell to all other atoms within the crystal.

Another way of looking at this mechanism is to imagine in which the valence electrons are not closely related along with individual atoms, but alter move around amongst the atoms inside the crystal. Thus, the individual atoms could "slip" over one another yet remain firmly held together through the electrostatic forces exerted through the electrons.  This is why most metals could be hammered within thin sheets (malleable) or drawn into thin wires (ductile).  While an electrical potential difference is applied and the electrons move freely among atoms, and a current flow.