NCEA Level 1 Chemistry: The reactivity series
Some metals are clearly very reactive. Sodium and lithium react violently with water and calcium dissolves quickly.
Other metals dissolve in acids and the rate at which they dissolve tells you something about how reactive they are. If they give off lots of bubbles rapidly they are reactive. Aluminium is out of order because it has a protective layer of oxide. It appeqars to be unreactive and this fact often crops up in NCEA level 1 exams.
A list of metals from the most reactive to the least reactive is known as the reactivity series.