[[1]] metal is preferred for the preparation of hydrogen gas from water.

The metals at the top of each group are the most reactive with ice or ice-cold water, forming the corresponding metal oxide and liberating hydrogen gas, according to the electrochemical series of the elements, where the elements are arranged according to their capacity to be reduced or oxidized. Therefore, because of their high reactivity, metals like sodium, potassium, and others cannot be used in the reaction that releases hydrogen gas. Once more, as we descend the group, the elements become less reactive, and metals like lead react with steam at extremely high temperatures to form the corresponding metal oxides and release hydrogen gas.

In electrochemical series, the elements lying above can reduce elements lying below them. To reduce hydrogen ions from water to hydrogen, any metal that lies above hydrogen in electrochemical series can be used. But sodium and potassium have a vigorous reaction even in cold conditions. Thus they are not used. On moving down the series reactivity decreases and Mg lies in the vicinity of hydrogen. So handling this reaction is easier. Thus Mg is preferred.