The groom wears the wedding ring on the left hand, just like the bride. Some people think this tradition derived from a Roman belief.
Supposedly, the Romans believed the ring finger on the left hand was particularly romantic. They believed it had a vein running to the heart. While biology has proven that is not true, the tradition lived on. Other theories about this tradition are more pragmatic. Some say the tradition began because most people are right-handed, and the ring sustains less damage if it is worn on the nondominant hand. Because it is the nondominant hand, the left hand has a smaller ring finger. It is often as much as a full-size smaller than the right-hand ring finger.