They differ in many ways, from their position or placement on the modern periodic table of elements, to all of their physical and chemical properties.
Mainly metals appear to the left side of the table whereas non metals appear to the right side.
Metals in terms of their appearance are illustrious, shiny, malleable and thus because of this appears in the solid phase, whereas non metals are dull, non malleable or ductile and generally are either liquids or gases.
In terms of their reactivity, metals will typically almost always lose electrons from their energy shells, whereas non metals will gain them to achieve a stable octet.