Octane would consist of discrete covalent molecules. [I don't like the sound of that, to be honest. The bonds between the atoms are covalent. I wouldn't describe the molecule as "covalent".]
Lithium bromide, like sodium chloride, potassium iodide [combine any of the group I elements with any of the group VII elements] are all lattices of oppositely charged ions (when below their melting points, obviously).