The metal that the priests of John’s tribe gather from the Dead Places symbolizes both the tribe’s developing understanding of technology and its reliance on superstitions. John never states outright why the tribe gathers metal, but we can assume that they use it to make weapons and tools. Even though the tribe has the skills and knowledge to use the metal that they gather, they also believe that the metal can only be collected by priests, and that touching the metal before it is ritually purified will kill anyone who is not a priest. The tribe’s superstition that metal is dangerous underlines Benét’s warning about the dangers of acquiring new knowledge; and by associating the metal with both knowledge and superstition, Benét indicates to readers that the boundary between knowledge and superstition may not be as distinct as we often believe.
Metal Quotes in By the Waters of Babylon
The north and the west and the south are good hunting ground, but it is forbidden to go east. It is forbidden to go to any of the Dead Places except to search for metal […] These are the rules and the laws; they are well made. It is forbidden to cross the great river and look upon the place that was the Place of the Gods—this is most strictly forbidden. We do not even say its name though we know its name.
There was a cooking-place but no wood, and though there was a machine to cook food, there was no place to put fire in it. Nor were there candles or lamps—there were things that looked like lamps but they had neither oil nor wick. All these things were magic, but I touched them and lived—the magic had gone out of them.