VIII. Gloria 

The Gloria is a joyful response to the forgiveness received in the Penitential Act. When it was first introduced to the Roman liturgy in 5th Century, it was sung only at the midnight celebration of the Nativity of our Lord. It is called the “Angelic Hymn” because it begins with the song of the angels that was heard at the birth of Jesus Christ.
x(The ‘Gloria’ is a very ancient and venerable hymn in which the Church, gathered together in the Holy Spirit, glorifies and entreats God the Father and the Lamb." (GIRM 53)

It is a basic creedal statement about the Church's belief in who God is and what He has done through the person of Jesus Christ. As Catholics, we believe in One God, who is a communion of three persons — the Almighty Father to whom the praise of the Sacred Liturgy is always directed; the Only Begotten Son, Our Lord Jesus Christ, who has become the sacrificial Lamb of God and takes away the sins of the world; and the Holy Spirit who is alone holy with the Son while radiating the glory of the Father.

Glory to God in the highest,Lk 2:14
and on earth peace to people of good will.

Here and during the Sanctus ("Holy, Holy, Holy") we take upon our lips the words of the angels. Joining our voices to the angels is a reminder that, in the Mass, Heaven and earth are mystically joined: "In the earthly liturgy we take part in a foretaste of [the] heavenly liturgy." (Vatican II, Sacrosanctum Concilium 8).

The “peace to people of good will” announced by the angels is one of the characteristics of the eternal covenant established through Jesus Christ: “I will make a covenant of peace with them; it shall be an everlasting covenant with them.” (Ezek 37:26)

The Gloria continues with praise of God the Father for His majesty:
We praise you, we bless you, Bar 3:6; Ps 145:2
we adore you, we glorify you, Rev 4:11; Rom 11:36; 1 Cor 6:20
we give you thanks for your great glory,1 Chr 16:24; 2 Cor 4:15
Lord God, heavenly King, Rev 4:8; Tob 13:7; Dan 4:37
O God, almighty Father. Gen 17:1; 2 Cor 6:18

Here we carry out two of the four ends of prayer: adoration and thanksgiving. We praise, bless, adore, glorify, and thank God for the glory He has revealed to us. It might seem a little repetitive, but those words do not all have the exact same meaning. The abundance of words is a reminder of how constant our praise of God should be. It is also a sign of our inability to describe our response to God’s greatness with just one or two words.

The next part focuses on God the Son, Jesus Christ: the Father and the Son are both invoked as “Lord God,” affirming the equality of the Father and the Son. After invoking Jesus by several of His titles, we pray a three-fold litany asking Him to have mercy on us and hear our prayers:

Lord Jesus Christ, Only Begotten Son,Jn 1:14,18
Lord God, Lamb of God, Son of the Father,Rev 1:8; Jn 1:29
you take away the sins of the world, have mercy on us;Jn 1:29
you take away the sins of the world, receive our prayer; Jn 14:13
you are seated at the right hand of the Father, Col 3:1; Heb 8:1  have mercy on us.

Through invoking Jesus by these titles, the Gloria describes our faith in Who Jesus is. This displays the catechetical power of the prayers of the Mass.

We again ask the Lord for mercy (twice) and we beseech Him to hear us when we pray. These four ends of prayer – adoration, thanksgiving, contrition, and petition – are summed up here in the hymn we sing most Sundays of the year. The Gloria, along with the Our Father, should be a model for personal prayer: glorify God and give Him thanks first, then present your needs to Him.

The hymn ends with a brief Trinitarian doxology. We profess the Son, the Spirit, and the Father as the one Holy and Most High Lord:

For you alone are the Holy One,Rev 15:4
you alone are the Lord, Isa 37:20
you alone are the Most High, Jesus Christ, Ps 83:18
with the Holy Spirit, Rom 8:9; 1 Pet 3:8
in the glory of God the Father. Amen.Lk 9:26; Jn 1:14; Phil 2:11

The word “alone” here might be misleading. It does not mean that Jesus is alone, for God is a living communion of three Persons, and neither the Father, nor the Son, nor the Holy Spirit can be “alone.” Rather, it means “only,” in the sense that there is only One Who is Holy, the Lord, the Most High, and that One is three Persons. The affirmation that Jesus Christ is the Most High is another clear identification of Jesus with God.

Because of the joyful nature of the Gloria, it is omitted in more somber occasions, such as the Advent or Lent. During those seasons, the Catholic Mass takes on a simpler and more penitent character.

The Collect: The opening prayer as the name indicates collect the prayerful intentions of the people who are gathered for worship. The Collect is packed with profound theology. It is compactly composed and generally includes an invocation of God and a description of what God has done , a specific petition and a conclusion that directs the prayer to the Father, through the Son and the communion of  the Spirit. The collect concludes the introductory part of the Mass.