How is hydrogen a metal

Solution -
Hydrogen is not a metal. Actually the above given series is a reactivity series .Hydrogen is included in this series  as it resembles alkali metals in some of its properties such as: It looses electron to form positive ion. The reactivity of hydrogen is taken as a reference to find the reactivity of other metals. Metals that are more reactive than hydrogen are placed above hydrogen and the metals that are less reactive than hydroen are placed below hydrogen