What happens when acids are added to the following?

(a) Metals

An acid is a substance in which the only positive ion is hydrogen.

A salt and hydrogen gas are produced when an acid reacts with a metal.

For example, hydrogen gas$\left({\mathrm{H}}_2\right)$ and zinc chloride$\left({\mathrm{ZnCl}}_2\right)$ are produced when zinc metal $\left(\mathrm{Zn}\right)$ reacts with hydrochloric acid $\left(\mathrm{HCl}\right)$.

The chemical reaction is as follows:

$\mathrm{Zn}\left(\mathrm{s}\right)+2\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{ZnCl}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$