Metals and non-metals will react with oxygen to form oxides. When the oxides are tested with universal indicator the have different properties. 

Metal oxides are alkaline.

Non-metal oxides are acidic.

Here is a power point

Watch this video on metals reacting with oxygen

Watch this video on non-metals reacting with oxygen

BBC Bitesize shows the difference between the chemical properties of metals & non-metals when they react with oxygen: www.bbc.co.uk/bitesize/guides/zqd2mp3/revision/4