Breaking Glass offers two meanings…
It reminds us of the destruction of the Holy Temple.
The breaking of the glass also is a warning of the frailty of a marriage.
That sometimes a single thoughtless act, breech of trust, or infidelity can damage a marriage in ways that are very difficult to undo – just as it would be so difficult to undo the breaking of this glass. Knowing that this marriage is permanent, the bride and groom should strive to show each other the love and respect befitting their spouse and love of their life.
Once the glass is broken, the guests rejoice, ‘Mazel Tov!’