Foundation needed for metal shed?

[BuildingNovice]

I know a foundation is recommended for a wooden shed, and assume the reason is to prevent damp rising and rotting the wood as well as maybe providing a level surface, which you may not get on grass.

Are these the only/right reasons?

So for a metal/plastic shed, would a foundation still be needed for levelling purposes only? If so, then what would be the least expensive and easiest way to provide a foundation.

I am thinking of getting a 4x6 or 8x6 foot shed.

 

[big-all]

dont get a metal shed iff the contents will be affected by damp
metal shed suffer badly from condensation