Keys
Jesus asks His disciples "who do you think I am."
Peter answers "You are the Christ or You are the Messiah."
Jesus replies "you are Peter (Petros=stone)"
"I [Jesus] am the bed rock (petra) and I [Jesus] will build My Church and the gates of Hades i.e. powers of death will not overcome it."
Jesus holds the keys and control of Death and Hades and he lives for ever and ever.
Keys denotes authority and power.
Hades is the Greek word for hell.
Background Reading:
Matthew 16:13-20
Keys - Key to the Kingdom, Peter's confession of Christ
13 When Jesus came to the region of Caesarea Philippi, he asked his disciples, "Who do people say the Son of Man is?"
14 They replied, "Some say John the Baptist; others say Elijah; and still others, Jeremiah or one of the prophets."
15 "But what about you?" he asked. "Who do you say I am?"
16 Simon Peter answered, "You are the Christ, the Son of the living God."
17 Jesus replied, "Blessed are you, Simon son of Jonah, for this was not revealed to you by man, but by my Father in heaven. 18 And I tell you that you are Peter, and on this rock I will build my church, and the gates of Hades will not overcome it. 19 I will give you the keys of the kingdom of heaven; whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven." 20 Then he warned his disciples not to tell anyone that he was the Christ.
also see Mark 8:27-30 Luke 9:18-21, Revelation1:18, Isaiah 22:22