Light
Jesus by saying "I Am" was telling the people that He was God.
Jesus said "I am the light of the world". Jesus was saying follow me not others, See Me and believe on Me you see God.
Background Reading:
John 8:12
Light
12 When Jesus spoke again to the people, he said, "I am the light of the world. Whoever follows me will never walk in darkness, but will have the light of life."