The formal beginning of the Mass is the entrance procession. Even if, for some reason, ministers do not enter a large procession from the back of the church, a formal entrance must be made. This entry is usually accompanied by a song. This song opens us to the action of the Holy Spirit. The General Instruction of the Roman Missal points out that singing is a way of showing and intensifying our unity with one another (GIRM 47), that is why the choir or cantor leads the assembly so that all together they sing this song of praise.
The Mass begins with a procession in which the celebrant and assistants approach the presbytery in procession, the order of the participants in the procession is established as follows: The thurifer with the smoking censer, when incense is used; the ministers or altar servers who carry the lighted candles and in the midst of them the acolyte or a minister carrying the processional cross; acolytes and other ministers; the deacon or, in his absence, the assigned lector carrying the Book of the Gospels elevated; and finally the priest who is going to celebrate Mass (GIRM 210).
Once the procession reaches the presbytery, the priest and all the members of the procession bow to the altar, the Book of the Gospels is placed on the altar, the priest and deacon approach the altar and kiss it at the same time, and depending on the occasion, the priest incenses the altar. All this is done because during the Mass, the altar represents Jesus Christ, as it carries in its mensa five crosses, one for each of the five wounds of Jesus Christ bore on the cross; when a church and its altar are consecrated, the altar is anointed by the bishop with the same oil that is used to consecrate the hands of priests and the heads of bishops (Dedication of a Church and an Altar 16a ). This is why, during Mass, reverence is made towards the altar.
Let us spiritually accompany the priest and his ministers during the entrance procession, for this also means for each of us a procession from our earthly nature to the Kingdom of God, from whom we will hear during Mass and share the banquet that He Himself has prepared for us so that we may have eternal life.