At weddings, the bride normally stands to the left of the groom so that his sword hand is free to defend against other suitors.
Brides normally stand on the left of the Groom at a wedding so that his sword hand is free to defend against any other suitors
Long ago, the right arm was considered the sword arm for most fighting men. If a man had to protect his bride, he would hold her with his left hand, and fight off attackers with his right arm.
The reason that men may have had to fight off others was because quite often women were kidnapped. The fact is that this tradition goes back to the old days where marriage was by “capture”.
This meant that the groom needed his right hand, which is his fighting hand, the hand he used to hold his sword, free just in-case he would ever need to defend his bride from other men that were interested in her and would object to the marriage to try to steal her away. There are some exceptions.
During a Jewish ceremony, the bride is often on the right and the groom is on the left. Other exceptions you may see are military and police weddings.