# What does the phrase "sea of electrons" describe?

$\text{Sea of electrons}$ probably refers to $\text{metallic bonding}$.
$\text{Metallic bonding}$ is typically described by a infinite lattice of closely-packed metallic atoms, in which each atom has contributed 1-2 (or more) electrons to the entire lattice. Because this results in the formation of $\text{positive ions}$ (why?), this lattice is held in position by electrostatic interaction between the positively charged ions, and the delocalized electron sea. Again, because the electrons are free to move thruout the entire lattice, this can account for the electrical and thermal conductivity of the bulk metal.
Because this bonding is clearly non-molecular, the bulk metal has properties as (typically with many electron metals), high melting point, and hardness, and (with all metals) $\text{malleability}$ and $\text{ductility}$, the ability of being hammered into a sheet, or being drawn into a wire - and these properties are why we value metals as building materials. In other words, the metal nuclei can move with respect to each other, WITHOUT disrupting the metallic bond.