At the end of the first chapter, there are two allusions to the biblical Book of Genesis:
And Lot’s wife, of course, was told not to look back where all those people and their homes had been. But she did look back, and I love her for that, because it was so human. So she was turned to a pillar of salt. So it goes. [...]
I’ve finished my war book now. The next one I write is going to be fun. This one is a failure, and had to be, since it was written by a pillar of salt.
The Book of Genesis explains that angels were going to punish the people of Sodom but wanted to spare Lot's family. Because Lot's wife turned and looked back, attempting to see the destruction wrought by the angels, she was turned into a pillar of salt. The narrator claims to love Lot's wife because to look back was human. For Vonnegut, then, to make mistakes, and to die as a result of those mistakes, is to be human. Considering the story centers around World War II, this humanizing message is quite relevant.
There is also a metaphor in the quotation above, as the narrator claims the story of Billy Pilgrim was written by a pillar of salt. The narrator, a stand-in for Vonnegut, then compares himself to the pillar of salt from Genesis: through reflecting and writing on his time as a soldier, he is constantly 'looking back' at destruction, and is punished accordingly. Vonnegut, by writing this book, is once again bearing witness to the horrors of war. The allusion to Lot's wife than reveals what Vonnegut thinks of himself as the author of Slaughterhouse-Five: a flawed human who has made and will make mistakes, complicit both as a real-life solider who fought in World War II and as voyeur in the horrors that he witnessed. The themes of witness and mercy, as well as war and destruction, are both furthered at the end of the first chapter through the allusion to the Book of Genesis.
Edgar Derby compares Howard Campbell Jr. to a series of lowly animals through metaphor, serving as a foil for Pilgrim as he does so:
His stance was that of a punch-drunk fighter. His head was down. His fists were out front, waiting for information and battle plan. Derby raised his head, called Campbell a snake. He corrected that. He said that snakes couldn’t help being snakes, and that Campbell, who could help being what he was, was something much lower than a snake or a rat—or even a blood-filled tick.
The above quotation takes place during the most virulent anti-Nazi, pro-Allied Powers moment in the story. By comparing Campbell to a snake, but then comparing him instead to a rat or a tick—a blood-sucking parasite—Derby condemns the American traitor and also the Nazi Party as a whole. The various animal metaphors suggest that Campbell is less than human. As an anti-war novel, Slaughterhouse-Five does not perpetuate an idealized perspective of World War II, which makes this moment stand out in particular. The conviction Derby shows in this scene contrasts sharply against Pilgrim's detached and resigned attitude.
Derby, however, dies in an ironic fashion, shot dead not for his ideals or for his country but for stealing a tea kettle. The book thus suggests that Derby's conviction is meaningless: wars do not reward those who fight in them, even if they fight for good reasons. Rather, it is Pilgrim's perspective that dominates the novel, and Derby serves as a foil only to ultimately support the narrator's perspective on war as a dreadful harbinger of death and destruction.