The electron sea model explains how metallic elements bond to each other. The valence electrons of each element are delocalized and are free to move around the fixed proton centers as if they were floating in a sea of electrons.
When metals bond to each other, they form a very different bond than if they were interacting with other elements. Metals have very few, if any, valence electrons in their outer s and p orbitals. As a result, the valance electrons are not bound tightly to the positive proton center. Instead of orbiting their respective metal atoms, the valence electrons delocalize. That is to say they, the valence electrons are free to wander around the entire metal complex.
Rather than being shared across a bond, or transferred, the valence electrons float in a sea of electrons, much like a water molecule floats free in the sea. Hence the term electron sea model is used to explain this movement of electrons in a metal bond.
The electron sea model explains the various properties of metals. For example, metals are good conductors of electricity because the valence electrons are free to flow throughout the whole structure and carry the electric current. This model also explains why metals are ductile and malleable. Because the valence electrons are not actually being shared between two elements, local bonds can easily be broken and reformed. That is why pure gold acts like putty in one's hand.