Matrimony was called by John Paul II the “primordial” sacrament. It is in effect a perfection of human marriage, in itself good. It can only be received by baptized Christians; when a baptized Christian marries an un-baptized person that may be a valid marriage, but is not a sacrament. Jesus defined Matrimony when he said “Moses allowed you to divorce because of the hardness of your hearts, but it was not so from the beginning.” and “For this reason a man shall leave father and mother and cling to his wife and the two become one flesh” and “In heaven there is neither marriage nor giving in marriage.” Saint Paul described Matrimony in the famous passage from the Epistle to the Ephesians, which begins “Husbands, love your wives as Christ loved the Church...”
The ministers of this sacrament are the husband and wife. In the early days of the Church the manner in which couples married varied from one place to another, but in general it reflected the customs of the local populace. Later, the Church began to require that the Sacrament take place in front of witnesses – an official witness from the Church (bishop, priest or deacon) and one other witness, a Catholic in good standing (usually bridesmaid or best man). If a Catholic marries a baptized protestant, it is possible to have a sacramental marriage with a protestant minister acting as the “official” witness, but requires the permission of the bishop.
The grace of Matrimony, drawn from the crucifixion, death, and resurrection of Jesus, helps the couple to overcome problems that arise, to be sources of growth and holiness to each other, and to realize the joy that comes from the gift of each to the other; and helps the couple form a family. The couple receives God's help so that they are able to reflect how Christ loves the Church.
The graces of Matrimony are related to the profound difference between a man and a woman (a difference that is even at the level of the soul), and because of this the Church holds that it is impossible for two individuals of the same sex to enter into the Sacrament.
To marry in the Catholic Church requires a period of discernment assisted by the Church (pre-Cana, a pre-marital inventory; meetings with the priest or deacon). The couple must be free to marry. The process by which this is assured is done by the priest or deacon. The best place to start is with a visit to the local pastor or his delegate, at least a year in advance of the time of the planned wedding.