A Catholic Mass has a particular format and specific requirements for music.
I hope you find the following outline useful.

Preludes: Music as guests arrive

Processional: Two or three pieces as the parents, bridal party and the bride enter

Words of Welcome

Old Testament Reading

Responsorial Psalm: This may be sung or read.  It must be from the book of Psalms and have a recurring refrain.

New Testament Reading

Gospel Acclamation: This is an alleluia, usually the “Celtic Alleluia,” since it’s widely known.
This music is changed for Lent and Advent.  If you don’t have a cantor then it may be said.

Reading of the Gospel

Homily

Sacrament of Marriage: Vows and Rings

Prayer of the Faithful

Presentation of Gifts: Music while the gifts are brought forward and the Priest prepares for Communion

Parts of the Mass: Often the Mass of Creation

Communion: Music while the congregation participates in Communion

Meditation: Music as Communion continues or while the Priest cleans up the alter

Closing Words and Presentation of the newly married couple

Recessional: Music for the couple and the bridal party to leave

Postludes: Music as guests exit the church

Music in a Catholic church needs to be sacred.  This means it must be liturgical or at least classical.
Pop tunes and Broadway loves songs will most likely not be allowed.

For a list of possible selections please click here: Ceremony Music Selections

I can cover a Catholic Mass on my own (harp and voice) or I’m happy to work with other musicians (organ, voice, etc).  Please check with your church to see if they require you to use their musicians.  If you wish to not have vocals for a Mass it is possible, but takes some adjustments.