JESUS DECLARES HIMSELF TO BE the "bread of life" (John 6:35), the "bread of God" (6:33).
The language is metaphorical, of course. That is made clear by John 6:35, where the metaphor is unpacked just a little: "I am the bread of life. He who comes to me will never go hungry, and he who believes in me will never be thirsty." One normally eats bread; one does not "come" to bread or "believe" in bread. Thus what Jesus means by eating this bread of life must be largely equivalent to what it means to come to Jesus and believe in him.
This "bread of life discourse" (as it is called) follows the feeding of the five thousand (6:1-15). There Jesus provides bread and fish to the hungry masses. These were the staple foods of Galilee; he provided what was needed to sustain life. But in this gospel the evangelist points out that Jesus' miracles are not mere events of power, they are significant: they point beyond themselves, like signs. This miracle points to the fact that Jesus not only provides bread, but rightly understood he is bread. He is the staple apart from which there is no real life at all.
Further, he is the ultimate "manna" (6:30-33). His interlocutors remind him that Moses provided manna, "bread from heaven" (Ex. 16), and they want him to do the same. After all, he had done it the day before in the feeding of the five thousand. If Jesus has performed the miracle once, why not again — and again and again? Isn't that what Moses did?
But Jesus insists the ultimate source of the "bread from heaven" was not Moses but God, and the ultimate "bread from heaven" was not the manna of the wilderness years, but the One who came down from heaven — Jesus himself. After all, everyone who ate the manna in the wilderness died. Those who eat the ultimate bread from heaven, the antitype of the manna, never die.
People in an agrarian culture understand that almost everything they eat is something that has died. We think of food as packaged things. The reality is that when you eat a hamburger, you are eating a dead cow, dead wheat, dead lettuce, dead tomatoes, dead onions, and so forth. The chief exception is the odd mineral, like salt. Jesus' audience, and John's readership, understood that other things die so that we may live; if those other things don't die, we do. Jesus gives his life so that we may live; either he dies, or we do. He is the true bread from heaven who gives his life "for the life of the world" (6:51).
Exodus 27; John 6; Proverbs 3; Galatians 2