A metal which does not react with nitrogen is :

Lithium shows exceptional behavior in reacting directly with nitrogen of air to form the nitride, Li₃N. Even Mg also forms magnesium nitride, when reacts with nitrogen gas.

Calcium and barium metals, owing to their reactivity with oxygen and nitrogen at elevated temperatures, have often been used to remove air from vacuum tubes.

Potassium (K) does not react with nitrogen gas, hence K stored in nitrogen gas.