Weddings and rings seem to be inseparable.
Nearly every culture uses a ring of some sort to signify marriage.
Not that the ring is always placed on the same finger the world over - in some parts of the world rings are placed around ankles or necks instead.
It is a very ancient custom that traces back well before the Romans who themselves used a ring to seal a marriage pact.
The marriage ring in this country is usually placed on the third finger of the left hand. To wear it on any other finger traditionally has a specific meaning, depending on the finger involved. -
First finger of the left hand means “I want to be married”.
Second finger means “I prefer platonic friendship”.
Third finger means “I am engaged or married”.
Little finger means “I never intend to marry”.
The choice of the third finger of the hand is no arbitrary choice.
Ancient philosophers maintained a very delicate nerve ran from this finger, directly to the heart. Later it was thought it was a small vein - the vena ainoris.
The left hand however has only been used in this country since the 16th century. Before then the wedding band was worn on the right.
In some European countries today, the wedding bands are exchanged at the engagement and worn on the right hand and then swapped over to the left hand at the actual wedding.
In these countries too, the engagement is considered almost as binding as the marriage, hence the use of a wedding band.