The ideal marriage gives a new, richer life brimming over with joy. John uses this as a metaphor for eternal life, the new kind of life that comes through relationship with Jesus. I think this metaphor is much more tightly woven into the tapestry of the gospel of John than most people have realized. This attempts to lay out some of the connections. Probably not everyone will agree with everything in here.
The first place where the wedding theme crops up is in John 2, when Jesus is invited to a wedding. The wine has run out. It was the responsibility of the groom to provide the wine (we know this from external evidence, and also from 2:10). Providing the wine was a large responsibility, because a wedding feast could go on for days and involve the whole town. His mother, who is probably there in some semi-official capacity, perhaps because she is a relation, asks him to help solve the problem. It is not clear from the text exactly what she was expecting, but I think it is unlikely that she was asking him to perform a miracle (though many interpreters have thought she was). More likely, she was assuming he would go somewhere to fetch more wine and would need the servants' help to bring it back.
What is particularly interesting is Jesus reply to her: "My hour is not yet come." If it were not for the use of that phrase in the rest of the gospel of John (see below on this), we would probably assume that he was saying, "This isn't my wedding--it's not my time to provide the wine." It is the bridegroom whose hour has come. Despite this, however, he does provide the wine, of surpassingly good quality. What are we to make of this?
The point of the story is not just that he performed a miracle. Note that the miraculous nature of it is de-emphasized--the miracle is buried in a dependent clause in 2:9, and apparently it is not at all dramatic; it reveals Jesus' glory only through later reflection. John calls it a "sign", and signs in the gospel of John are never merely demonstrations of power. In every case, they point to something beyond the act itself, and the kind of power exerted reveals something about who Jesus is. (For example, he makes physical bread and then says, "I am the bread of life"--the miraculous physical bread is intended to be a picture of the spiritual bread that he is always giving.) Here, I think that the sign is that by providing the wine, he is acting in the role of the bridegroom. Jesus is the true bridegroom, the one who will provide the best possible wine and the most satisfying relationship. This is how he reveals his glory.
In case the allusions in the story of the wedding at Cana are too subtle and a reader misses it, in 3:29 John tells us flat out that Jesus is the bridegroom of the people of Israel. (Note that this happens in the context of a discussion about water for baptism and purification, probably intended as a link to the water for purification that Jesus turned into wine.) In the Old Testament, Yahweh himself is the husband of his people (Is. 49-50, 54, various other passages; Jer. 2; Ezek. 16; Hos. 1-3). The relationship went tragically wrong through Israel's infidelity, and Yahweh distanced himself. But those same prophets promised a time when he would no longer be distant. For over six hundred years the faithful among his people waited. Then Jesus walked on the earth, and the people flocked to him. 3:29 explains this as the bride following the bridegroom. Finally the time has come.
The image of the bridegroom takes an unexpected twist, however, in the next chapter. An important Old Testament image, deeply ingrained into Jewish thinking, is the picture of a man meeting his future wife at a well in the heat of the day and drawing water. Abraham's servant meets Rebecca; Jacob meets Rachel; Moses meets Zipporah. This boy-meets-girl-at-well picture probably had a strong grasp on the imagination because water from a well in an arid land is like the refreshment that the marriage relationship brings. (See Prov. 5:15-20 as an example of this imagery.) Like these Old Testament characters, Jesus also meets a woman at a well at noon, and as in those stories, there is an exchange of water. Primed by this Old Testament motif, and by John's statements about the bridegroom in the previous chapter, we are thinking of a marriage. But the woman here is a shockingly unsuitable bride for a Jewish rabbi: she is a Samaritan, married five times, living currently in adultery. And that is the point: the bride of Christ, the bride of Yahweh, will consist not only of the people who were thought to be suitable, but all the people who come. Jesus offers her living water (probably the same symbolic idea as the better wine at the wedding of Cana), which is what she has really been seeking all along through her failed attempts at marriage relationships. Just like the people of Israel who John says are flocking to the bridegroom (3:26), all the Samaritans came out to him (4:30). He is happy to stay with the Samaritans (4:40) as he did with his disciples after the earlier wedding (2:12). The story concludes with the Samaritans saying that Jesus truly is the savior of the world (not just Israel).
The picture of the wedding is probably also behind Jesus' words in John 14, "I go to prepare a place for you. In my Father's house are many rooms.... and I will come again to take you back to myself." A young man would often add an additional room on to his father's house when he was about to be married, and only when the place was prepared would he come and get his bride. The upper room discourse goes on to talk about how the disciples will bear fruit only so long as they remain in relationship with him--probably an allusion to fruitfulness in marriage, an idea that Paul uses more explicitly in Romans 7.
The wedding and the hour
Later that night, Jesus prays, "Father, the hour has come! Glorify your son, that your son may glorify you." (John 17:1) These words echo key phrases from the story of the wedding at Cana (2:4 and 2:11). Given how carefully the gospel of John is constructed, this is unlikely to be a coincidence. Everywhere else in the gospel of John, "the hour" refers unambiguously to his death; why does he use that phrase in talking to his mother at the wedding?
Jesus left his Father to become one with his bride, as it says in Genesis, "A man shall leave his father and mother, and be united to his wife, and they will become one flesh." A man starts out as one flesh with his parents, and becomes one flesh with his wife. This is what he is praying for in chapter 17: that he and his disciples may be one, as he and the father are one. His "hour" is the time when the union with his people is accomplished. It is both his wedding (which ch. 2 suggests) and his death, because his death accomplishes the union.
It seems rather grisly to connect the crucifixion to a marriage, but I think that is precisely what John is doing with a number of ironic symbols. He says, "I am thirsty," just as he said to the Samaritan woman. He drinks sour wine, not the good wine that he provided at the wedding. He is wearing a crown, which the bridegroom would do at a Jewish wedding--but it is not a garland, it is a crown of thorns.
At his death, blood and water flow out of his side. Commentators stumble over what to do with this emphatic assertion; sometimes it is taken to mean that he clearly died, a form of medical evidence. (Though it is by no means clear--just what precisely does it mean that the blood had separated into two parts? And would most readers in the first century have understood that?) But it would be out of character for John, in his highly symbolic and theological gospel, at the very high point of the narrative, to suddenly forsake his theological mind and emphasize purely medical facts. The medical facts are there, perhaps, but are unlikely to exhaust the significance.
I think the blood and water flowing out of his side is a symbolic, pictorial fulfillment of the better wine and the living water that Jesus promised. The argument here is a bit technical, so bear with me or just skip ahead. I think we are supposed to link together most of the references to water, wine, and blood in the gospel of John; the author is careful about his symbolic references, and is not throwing out symbols willy-nilly. These all refer to the new quality of life that comes through relationship with him--more specifically, through the Spirit that he gives, as 7:37 makes clear. There is an interesting translation issue in 7:37, having to do with where punctuation is placed in the sentence (there was no punctuation at all in the original manuscripts, so where punctuation is placed is a translator's decision). Most English translations of 7:37 follow the eastern fathers: "If anyone is thirsty, let him come to me and drink. Whoever believes in me, as the scripture has said, out of his belly shall flow rivers of living water." Here the water flows from the believers. But by changing the location of the period, we have the western Fathers' understanding of the verse: "If anyone is thirsty, let him come to me. And whoever believes in me, let him drink. As the scripture has said, 'Out of his belly shall flow rivers of living water.'" In this case, water flows from Jesus, which I think is a much more natural way of understanding the passage. 7:38 clarifies that this water is referring to the Spirit that was going to come when Jesus was glorified--which in John's gospel happens on the cross, the ultimate glorification of Jesus. Only with this interpretation of 7:37 is John's emphatic insistence on the water that flowed from Jesus' side understandable (19:35--he repeats it three times). It is a physical sign of the spiritual reality that because of his death, the Spirit is now available to believers. This is the time, at least in a picture, when he provides the better wine that he promised back at the wedding of Cana, and the living water that he promised to the Samaritan woman.
In our lives, marriage is the only thing that can change a person's family after he is born. John makes it clear in several places that after the cross, the disciples are part of Jesus' family in a way that they were not before. Interestingly, Jesus mother appears in only two places in the gospel: at the wedding, and at the cross. In both places, he addresses her with the same title ("Woman", a not-entirely-common way of talking to a mother, something which commentators stumble over). At the cross, he makes a point of bringing the disciple Jesus loved (despite all the arguments over this, I still think this is John himself) and his mother together into the same family. Perhaps the most common view of Jesus' words here is that they show the extent of Jesus' love: even in his extremity, he could still think about his mother's well-being. This may be true, but I am fairly certain it does not exhaust the meaning. John is primarily thinking theologically rather than psychologically. I think what we are supposed to gather from this is that the disciple whom Jesus loves is now part of his family--just as the woman a man loves becomes a part of his family. John uses this concrete picture of changed family relations to show what is happening spiritually.
There is probably another allusion to marriage in the scene with Mary Magdalene in the garden. Once again, a garden scene with a man and a woman is a rich picture for a Jewish audience, with overtones of the original garden. Mary goes so far as to grab him and hug him (20:17), definitely overstepping the bounds of propriety. This does not mean that they had some kind of physical relationship, contra the silly speculations that have recently become popular; but the text really does have hints of something romantic. I think that John is using the suggestive image to point out that Jesus and Mary now have a kind of relationship which in some ways is a marriage (though not a physical marriage), a relationship which they did not have before the cross. In the next verse, he calls his disciples "my brothers" and he calls God "your father"; never before had he done either of these in the gospel of John. It is only after the cross that they are his brothers, and they have a common father in this sense--they have been brought into Jesus' family.
Finally, the gospel concludes with Jesus asking Peter if he loves him. This is the only suitable attitude if we are the bride of Christ.