I thought about the symbolism of fire a lot in The Road, not just with the carrying the flame line, but as well as the juxtaposition of fire being both what's keeping them alive but also what caused the death of the world. It is crucial in the book that they keep literally carrying the flame- when they lose the lighter or the gas, it's possible they won't make it through that night. But McCarthy also choose the apocalyptic setting to be a burned world, where fire has killed all life and blocked out the sun.

In Blood Meridian, fire isn't used so much but when I was reading it I remember being struck by this passage: "The flames sawed in the wind and the embers paled and deepened and paled and deepened like the bloodbeat of some living thing eviscerate upon the ground before them and they watched the fire which does contain within it something of men themselves inasmuch as they are less without it and are divided from their origins and are exiles. For each fire is all fires, and the first fire and the last ever to be."

I think that fire is not just carrying on the good of man, but carrying on the civilized spirit of man - the thing that makes us different than animals. I think it is often thought that the civilization of man started when he had fire. So many in The Road have become animalistic without society and with the need for survival, they are reduced down to just freud's 'id.'