Is it Sunnat for a man to wear a ring?
Many Fuqahaa and Muhadditheen state that Rasulullah sallallahu alaihi wasallam wore the ring out of necessity (to stamp his letters) .Therefore the Sunnat is for one who would have some necessity in wearing a ring (e.g. a Khalifa /Ruler).
As for those who do not have any need for it, it would be merely permissible.
However, the permissibility revolves around the following factors:
It is better to wear the ring on the left hand and it should be worn on the little finger. If the ring has a stone with it then the stone should be facing the inside of the palm.
And Allah Ta’aala knows best.