What is the difference in their physical properties between solids with a molecular and non-molecular structure?

Solids can have a molecular crystal lattice and non-molecular (atomic, ionic, metallic).

Solids of molecular structure have low melting points, their solutions do not conduct electric current, since they do not contain charged particles.

Substances with a non-molecular structure are very solid and have high melting points. Metals conduct electric current, substances with an ionic lattice are electrolytes, and those with an atomic lattice are the hardest ones, such as diamond.