Final answer:
The electron sea theory postulates that in a metal's structure, some valence electrons are delocalized and free to move around, creating a sea of electrons that binds the positively charged metal ions together.
Step-by-step explanation:
According to the electron sea theory, when a collection of metal atoms are in close proximity to each other, some electrons float amongst the atoms. This model envisions that the metal atoms release some of their valence electrons, which then become delocalized and are free to move throughout the entire structure of the metal. The positively charged metal ions are held together by a sea of these free-moving, delocalized electrons, which can easily conduct electricity and heat. This forms a metallic bond and gives metals their unique properties, such as electrical conductivity, ductility, and malleability.