Q: Is the Gloria required to be sung at weddings? Does the rubric assume that the Mass to be celebrated will satisfy the Sunday obligation and serves as a vigil, thus the Gloria is sung?
A: The third edition of the roman missal added the Gloria to sacramental celebrations such as weddings and confirmations. Even a wedding on a weekday in Lent will now have a Gloria, much as the Solemnity of St. Joseph or the Annunciation does.
Any Saturday evening mass fulfills the canonical obligation to participate in mass on Sunday. It doesn’t matter which readings or prayers are said, or if the Gloria is sung – it’s just a question of the day and time.