In metallic solids, the structural unit is a lattice of positive ions submerged in a "sea" of mobile valence electrons. The positive ions are the atoms that have lost their valence electrons, while the valence electrons are the electrons that are no longer bound to any particular atom. The lattice of positive ions is held together by the electrostatic attraction between the positive ions and the negative valence electrons.

Metallic solids are characterized by their high electrical and thermal conductivity. The high electrical conductivity is due to the fact that the valence electrons are mobile and can easily move through the lattice. The high thermal conductivity is due to the fact that the valence electrons can easily transfer heat from one part of the lattice to another.

Metallic solids are also characterized by their malleability and ductility. Malleability is the ability of a material to be hammered into thin sheets, while ductility is the ability of a material to be drawn into thin wires. The malleability and ductility of metallic solids are due to the fact that the lattice of positive ions is not rigid. The positive ions can easily move past each other, which allows the metal to be deformed without breaking.

The strength of a metallic solid depends on the strength of the electrostatic attraction between the positive ions and the valence electrons. The stronger the electrostatic attraction, the stronger the metal will be.