The weight of the “things” in Tim O’Brien’s story is physical, emotional, and psychological. There is generally not a direct correlation between physical and the other kinds of burdens. In many cases, the lighter the physical burden, the weightier is its emotional impact.
One could begin by examining the weight that O’Brien, as the author, carries. Through the character of the narrator, he shows that remembering traumatic events and then figuring out a way to tell them is a burden that a writer needs to find a way to unload.
The individual soldiers in the unit may carry light, tiny things in physical terms, such as a photograph, but the image of a loved one can present a tremendous emotional weight. This is the situation for Jimmy Cross, who treasures the photo of his distant girlfriend.
For others, their physical strength becomes a liability rather than an asset, as they are charged with carrying the heavy gear on which the other soldiers also demand. This applies to both Henry Dobbins and Ted Lavender, but in different ways. Because he is a big man, it falls to Henry to carry the machine gun. When Ted Lavender was shot and killed, the worst thing he carried was weightless, thought the other things had both weight and bulk:
more than 20 pounds of ammunition, plus the flak jacket and helmet and rations and water and toilet paper and tranquilizers and all the rest, plus the unweighted fear.
Guilt is another type of “thing” that may be, as O’Brien presents it, one of the heaviest weights because of its persistence. This is what relentlessly haunts Cross, who cannot shake the feeling that he caused Ted’s death.