Here's why:

* Structure: Sodium atoms are arranged in a regular, repeating pattern called a body-centered cubic lattice.

* Bonding: Sodium atoms are held together by metallic bonds, which involve a "sea" of delocalized electrons. These electrons can move freely throughout the structure, contributing to sodium's properties.

* Properties: Metallic solids typically exhibit high electrical and thermal conductivity, malleability, and ductility. Sodium demonstrates all of these properties.