The metal which is stored in kerosene

Sodium more reactive metal, it can easily react with oxygen and form oxide to prevent this we have to keep it under kerosene.

Sodium can easily react with oxygen and moisture and forms sodium oxide with the liberation of ${\text{H}}_{\text{2}}$ gas.  This reaction is an explosive reaction because of the high reactivity of sodium.  So Na metal should be stored in kerosene.

${\text{2Na + H}}_{\text{2}}{\text{O}}_{\left(\text{Cold}\right)}\to {\text{Na}}_{\text{2}}\text{O}+{\text{H}}_{\text{2}}\left(g\right)\uparrow$ .