The Church has two functions: The Body of Christ, with Chirst as the Head and the Bride of Christ, with Christ as the Bridegroom.
Here is a good picture of the First Century Church at its beginnings:
Acts 4:32-37
All the believers were one in heart and mind. No one claimed that any of his possessions was his own, but they shared everything they had. With great power the apostles continued to testify to the resurrection of the Lord Jesus, and much grace was upon them all. There were no needy persons among them. For from time to time those who owned lands or houses sold them, brought the money from the sales and put it at the apostles' feet, and it was distributed to anyone as he had need.
Joseph, a Levite from Cyprus, whom the apostles called Barnabas (which means Son of Encouragement), sold a field he owned and brought the money and put it at the apostles' feet.
1Cor 12 is a great explaination of the Church as the Body of Christ.
Ephesians 5 talks about the Church as the Bride of Christ.
The Great Commission is another place to look for what actions the church should be taking in the world.
Matthew 28:18-20
Jesus came and told his disciples, I have been given all authority in heaven and on earth. Therefore, go and make disciples of all the nations,[
b] baptizing them in the name of the Father and the Son and the Holy Spirit. Teach these new disciples to obey all the commands I have given you. And be sure of this: I am with you always, even to the end of the age.
Mark 16:15-18
He said to them, "Go into all the world and preach the good news to all creation. Whoever believes and is baptized will be saved, but whoever does not believe will be condemned. And these signs will accompany those who believe: In my name they will drive out demons; they will speak in new tongues; they will pick up snakes with their hands; and when they drink deadly poison, it will not hurt them at all; they will place their hands on sick people, and they will get well."
The modern Church is doing the best it can to fulfill and carryout her roles and functions in todays world. As in the book of Acts however, (and warned about in the gospels) those will come in the name of Jesus claiming to be doing God's work and really be an imposter. We, as the Church are charged to be in the world, but not of the world. I see daily the men and women who are truly laying down their life for others and who sincerely love the Lord. I see miracles happen, still to this day. People are being healed of their sicknesses, demons are being cast out of people, the message of the gospel is being preached by many.
As we approach the Return of Christ, those who are out to decieve the world about God will infect this world more and more.