When you think of a bond, you probably think of the "ball and stick" model of bonding where there are two atoms connected by one or more bonds. The bonds between those two atoms connect only those two atoms. Because the bond just stays put, it's referred to as localized covalent bonding.
However, metals do different stuff. If you've got a metal, you've got a great big bunch of atoms all held together in a great big bunch of valence electrons. Rather than two valence electrons forming a single bond between two metal atoms, you have all of the valence electrons from every atom in the element moving around all over the place in delocalized bonds. If you imagine putting a bunch of pieces of Velcro into a pile of yarn, the electrons are represented by the disordered yarn and the metal atoms are represented by the Velcro.
