Now my question to you... How important to the Body of Christ is the message of the Kingdom of God? Frankly, we have nothing else to preach or teach. The message of the Kingdom is good news, and the Church exists to proclaim it. Now, if we are doing our job, everything we are about will be Kingdom-focused: every sermon we preach, every Bible study we teach, every ministry we perform, every activity we accomplish and every worship service we celebrate.
Keep in mind, that the Kingdom of God must be our highest priority; Jesus gave us no other commission. When He said, "Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and the Holy Spirit." (Matthew 28:19) He was commanding us to proclaim the Kingdom of God to a world that knew it not. He wasn't commanding us to spread another religion called "Christianity". Although the world is very familiar with the regimes of men, it is essentially ignorant of God's Kingdom. People of every nation need to know that God's Kingdom has come to Earth, and that faith in Jesus Christ as Savior and Lord is the way in.