Write the chemical reaction when metals …

Metals react with acids to form salt and hydrogen gas.

Metal + Dilute acid →  Salt + Hydrogen

Metals react with dilute hydrochloric acid to give metal chloride and hydrogen gas. Example - Magnesium reacts violently with dilute hydrochloric acid to form magnesium chloride and hydrogen.

Metals react  with  water to produce metal oxides with the release of hydrogen gas. But all metals do not react with water.

Metal +  Water → Metal oxide + Hydrogen

Metal oxides that are soluble in water dissolve in it to further form metal hydroxide.

Metal oxide +  Water → Metal hydroxide

Metals  such as  sodium  and  potassium  react  vigorously  with  cold  water  to  lead  to  evolution  of hydrogen, which immediately catches fire producing a large quantity of heat.

Metals react with acids to form salt and hydrogen gas.

Metal + Dilute acid →  Salt + Hydrogen

Metals react with dilute hydrochloric acid to give metal chloride and hydrogen gas. Example - Magnesium reacts violently with dilute hydrochloric acid to form magnesium chloride and hydrogen.