Simon Peter had just confessed that he believed that Jesus was the Christ, the Son of the living God (Matthew 16:13-16).  It was a huge statement and maybe it even surprised the brazen fisherman.  Peter’s confident announcement owed nothing to his intellect or Bible knowledge.  The truth came from God the Father as a gift to Peter; he could see exactly who Jesus was.  As he grasped the truth by faith, Jesus gave him a new name, Peter, which means ‘Rock’.  Of course, Jesus is the unchangeably secure Rock (Matthew 7:24), but everybody who trusts in Him is made unshakable and unashamed (2 Timothy 1:12). 
 
It was God’s choice to place His gospel mission into the hands of a few men who were convinced of the identity of Jesus as the Son of God.  The mission of the church would depend on the apostles’ teaching (Matthew 28:18-20).   The 'keys of the kingdom' are the gospel truths which free people from evil lies which act as barriers to faith.  When the apostles announced freedom from sin, Satan and hell through the gospel, all heaven would agree. That continues to be the work of the church. 

The gospel they preached was that Jesus Christ, who was crucified, was God in a human body; and that His resurrection demonstrated the eternal life which would be given to all who believe in Jesus (Acts 2:22-24).  That truth, and the faith God would give to those who heard the message, was so secure that it would act as a battering ram to break down Satan's strongholds forcing him to release people he has held captive (2 Corinthians 10:3-5).
 
Every believer has the right, and shares in the apostolic commission, (Matthew 28:18-20) to announce Jesus as God the Son to a spiritually sick and dying world.  As you grow in confidence that what you have believed about Jesus is also eternally important for your friends and colleagues, you must share it – and pray that God will give them the ability to believe and develop a rock-solid saving faith.