What does metallic bonding primarily involve?

Metallic bonding primarily involves the bonding of metals into pure solids or solid solutions. In metallic bonds, atoms within a metal lose their outermost electrons, creating a "sea of electrons" that are free to move around the lattice structure of positively charged metal ions. This delocalization of electrons allows metals to conduct electricity and heat efficiently and gives them their characteristic malleability and ductility.

The option describing metallic bonding as the bonding of metals into pure solids or solid solutions accurately reflects this phenomenon, as metals tend to form crystalline structures where these bonds manifest, either in a pure form or as mixtures (solid solutions) with other metals.

The other options fail to capture the essence of metallic bonding. A lattice of non-overlapping atomic orbitals describes covalent bonding more appropriately, where electrons are shared in specific pairs. The idea of a combination of ionic and covalent bonding pertains to compounds formed by different types of chemical bonds, but does not define metallic bonding, which is unique in its characteristics. Lastly, electron-sharing within isolated molecules pertains to molecular covalent bonds rather than the delocalized electron behavior seen in metals.