Aluminium is a metal, and so the aluminium engages in metallic bonding. This is where the valence (outer) electrons of the atoms dissociate (come away) from their atoms and move freely throughout the metal structure, creating bonding between the atoms.
This is why metals can support an electric current, for example copper wiring - because when a potential difference is applied to the metal, electrons can move freely throughout the structure, and so can flow from e.g. a battery to a lightbulb.
