A reactive metal is one that readily reacts with other elements to give up its electrons. The most reactive metals will react even with water, while the least reactive will not react, even with concentrated acid.
In a reactivity series, the most reactive element is placed at the top and the least reactive element at the bottom. More reactive metals have a greater tendency to lose electrons and form positive ions and the most reactive metals are able to donate electrons to the ion of the less reactive metal in a displacement reaction.
Some examples are galvanised steel (when steel is coated in a layer of zinc or nickel to prevent corrosion), electro plating (when a more reactive metal is placed in an aqueous (water solution) with a salt of a more reactive metal and electricity is passed through it to coat the other substance), sacrificial protection of metals (the protection of iron or steel against corrosion by using a more reactive metal), displacement reaction (when copper in copper sulfate solution coats an iron nail) and the extraction of aluminium.
Only metal carbonates of metals in group 2 undergo thermal decomposition to produce a metal oxide and carbon dioxide.