Traditionally, men in the United States wear their wedding ring on the left hand on the "ring" finger. This is the finger closest to the little finger
See more men's wedding rings.
It was a common belief in the middle ages that you had a vein running from your left hand ring finger to your heart, which is how this specific tradition was started.
While there is no exact and proper guidance for which finger is the correct one, most people choose to use their religious or family traditions to determine which finger to choose.