Question

odd man out iron, nickel, copper, cobalt

Answer 1

Copper... Bcoz Others contain magnetic energy....

Answer 2

The answer of your question is "copper" 
This is because the nickel, cobalt as well as the iron are the magnetic  metals while the copper is non-magnetic 
Copper is actually the very weak magnetic element hence generally termed as the non-magnetic one. The most of metals are non-magnetic in nature . Only the element like nickel, cobalt, iron  as well as the gadolinium and neodymium etc are the magnetic elements. These are attracted towards the magnet or have ability to magnetized .