Are metal and non-metal acidic or basic in nature?

Most metal oxides react with water to give hydroxides (compounds containing the OH− ion) and resultant basic solutions.

Examples: Sodium and magnesium oxides are alkaline. Aluminium oxides are amphoteric (reacting both as a base or acid). 

Most nonmetal oxides react with water to form acids and resultant acidic solutions.

Examples: Silicon, phosphorus, sulphur, and chlorine oxides are acidic in nature.