In the Order of Worship/Service, what is essential?

>>>I thought I'd throw this thought out into the light of day. In our various church backgrounds, what do you consider as essential in your Order of Worship and what parts are secondary (indifferent) or to say, may help and not harm a Worship Service?<<<

Interesting question. The only parts of the Catholic worship service which seem to be universal and which go back to the earliest times are:

1. Scripture reading and the doctrine of the Apostles.
2. the breaking of the bread.
3. prayers.

We can see this in the very first Liturgy which Jesus conducted after He rose from the dead:

Luke 24:25Then he said unto them, O fools, and slow of heart to believe all that the prophets have spoken: 26Ought not Christ to have suffered these things, and to enter into his glory? 27And beginning at Moses and all the prophets, he expounded unto them in all the scriptures the things concerning himself. 28And they drew nigh unto the village, whither they went: and he made as though he would have gone further. 29But they constrained him, saying, Abide with us: for it is toward evening, and the day is far spent. And he went in to tarry with them. 30And it came to pass, as he sat at meat with them, he took bread, and blessed it, and brake, and gave to them. 31And their eyes were opened, and they knew him; and he vanished out of their sight. 32And they said one to another, Did not our heart burn within us, while he talked with us by the way, and while he opened to us the scriptures?

And we see that the Apostles continued in that custom:
Acts 2:42
And they continued stedfastly in the apostles' doctrine and fellowship, and in breaking of bread, and in prayers.

>>>What is the main reason you attend church?<<<

The main reason why I attend Church is because I love Christ.

Scripture is clear that we are one body. Christ didn't come for us to save us separately but to incorporate us into Himself.

The Church is that body into which He incorporated us. The Church is that authority which He established to guide us to heaven.

Psalm 133:1
Behold, how good and how pleasant it is for brethren to dwell together in unity! 2It is like the precious ointment upon the head, that ran down upon the beard, even Aaron's beard: that went down to the skirts of his garments;
3As the dew of Hermon, and as the dew that descended upon the mountains of Zion: for there the LORD commanded the blessing, even life for evermore.

It is in the Liturgy of the Church that we join ourselves to the heavenly Liturgy with the Angels and Saints praising God.

Romans 15:6
That ye may with one mind and one mouth glorify God, even the Father of our Lord Jesus Christ.