Declare His glory among the nations, His wonders among all peoples.For the LORD is great and greatly to be praised; He is also to be feared above all gods. 1 Chronicles 16:24-25 (NKJV)
The mission of the Church is two-fold.
First it is Doxilogical - The church exist to declare the glory of God. This is the purpose of each individual Christian, each local congregation, and the Church as a corporate whole.
The second mission of the Church is Missiological - The church exists to proclaim God's works, wonders, and Gospel to ALL peoples (nations).
The very last command given to the Apostles (and the church) is to make disciples...
"And Jesus came and spoke to them, saying, "All authority has been given to Me in heaven and on earth. Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all things that I have commanded you; and lo, I am with you always, even to the end of the age." Amen." (Matthew 28:18–20, NKJV)
To accomplish this mission Jesus Christ provided servant-leaders...
And He Himself gave some to be apostles, some prophets, some evangelists, and some pastors and teachers, for the equipping of the saints for the work of ministry, for the edifying of the body of Christ, till we all come to the unity of the faith and of the knowledge of the Son of God, to a perfect man, to the measure of the stature of the fullness of Christ. Ephesians 4:11-13 (NKJV)
The function of the "pastor-teacher" is also two-fold:
"for the equipping of the saints" in order for the saints, the individual Christian, to do "the work of the ministry"
and "for the edifying of the body of Christ", that is the building up, strengthening of the church and each individual believer towards Christlikeness.
So, the mission of the church is to declare God's Glory, Proclaiming to the Nations, Making Disciples.