All acids contain hydrogen, therefore it is essentially to note that each time one of these reactions occurs, Hydrogen gas will always be one of the products, and the other will always be a salt. Acid + Metal -> Salt + HydrogenThe salt formed will depend on what acid and what metal is used. For example; Nitric acid will form Nitrate salts and Hydrochloric acid will for Chloride salts. Each time the negative ion from the acid, e.g. Cl- will combine with the positive metal ion to form a salt. For example:Ca + 2HCL -> CaCl2 +H2 Remeber to look at what the group number of the metal is in order to determine its charge as an ion.