God gave you some of his authority by delegating it to you. You are to use it in his behalf, that is, in his name. You are to use it as he would, that is, to do kingdom business. Consider for a moment the keys you use to open the door to your home or to start your car. Keys are pretty ordinary and in today's culture they are essential.
Keys have specific purposes.
Second, access to something of value implies a certain amount of responsibility for the way you use it. Giving someone a key is a sign of trust, privilege and responsibility. Based on the universal significance of keys, we can conclude that Jesus was giving Peter access to the treasures of heaven. As we mentioned earlier, giving someone a key clearly implies a certain amount of trust and responsibility.