The Sacrament of Marriage is a covenant, which is more than a contract. Covenant always expresses a relationship between persons. The marriage covenant refers to the relationship between the husband and wife, a permanent union of persons capable of knowing and loving each other and God. The celebration of marriage is also a liturgical act, appropriately held in a public liturgy at church. Catholics are urged to celebrate their marriage within the Eucharistic Liturgy.
~from the United States Catholic Catechism for Adults
Because of the great value that we give to the Sacrament of Marriage and the centrality that the Eucharist has in our belief system, it is strongly recommended that marriage be celebrated in the context of a Mass. This can be done even if one of the two parties is not Catholic. The Catholic Church asks you to seriously prepare for your wedding and marriage.
"The intimate communion of life and love which constitutes the married state has been established by the creator.... The matrimonial covenant...has been raised by Christ the Lord to the dignity of a sacrament." (Catechism of the Catholic Church, #1601, 1603)