Final answer:
A similarity between covalent and metallic bonding is that they can link atoms into periodic lattices.
Step-by-step explanation:
A similarity between covalent and metallic bonding is that they can link atoms into periodic lattices. In covalent bonding, atoms share electrons to form a stable bond between them. In metallic bonding, valence electrons are delocalized, creating a 'sea' of electrons that can freely move throughout the metal lattice.