They are all symbolisms in weddings and they are just needed to represent the couple in their wedding day. Whether it sounds superstitious or not, our relationship does not depend on such symbols. It is still the obligation of the couple to do their responsibilities to their spouse and it is still God who should be at the center of every relationship.
Now going back to the question of the purpose of having such items, well it is all traditional. This is just my opinion about the Unity Candle, the Cord and the Veil in wedding ceremonies. Most of what your secondary sponsors would be playing a role in your wedding is the participation of each on what item should they handle. I don’t know where it all started on these symbolisms but it has been running from generations to generations of every supposedly “Christian weddings”.
A unity candle lights the way of the couple while the cord symbolizes as the one that will bind the couple and the veil as to cover both the couple in unity and purity. Whether this is true or not, it will just depend on the couple. The most important thing here is the love and respect of each other and how they will nourish that love to continue on as long as they live.
It is the responsibility of each (bride and the groom) to make the relationship work. It is not how much you spend on your wedding day, or on how much does the candle worth or what is the design of your cord and how long and strong is your veil. These items only symbolizes of what a couple should be looking forward but does not signify whether their relationship would last for long since I have seen a lot of couples who tied the knot particularly celebrities who have extravagant weddings but ended up in divorce which God hates.
I have nothing against celebrity weddings. I have just stated an example that it is not the amount of the wedding that is worth; it is the presence of God and your family that witnesses the unity of the couple who exchanges their vow. A Unity Candle by the way is the one that both the male and female candle sponsors light up together. I have heard long time back that it is bad to see a candle being flamed off after it was being light up, since they say that one of the couple will die. Well, in reality all people will die, no one knows when and that issue is of course not true, whether a candle would be flamed off or not.
About the Cord, well it is composed of gold coins and some uses a white braided cord (the usual one). Whether the cord breaks off, it has nothing to do with the broken vows or relationship of the couple. Again as I can say, this is another fallacy. Our marriage does not depend on the cord that we used during the wedding. So don’t be so superstitious about it including the veil. Be more concern on how to keep the vow you made before God. Both couple should work hand in hand in order to keep the marriage long lasting.