Laura describes a city as if it were a zoo of living creatures. Ordinary things are turned into animals: underground trains become silvery snakes that shriek, with commuters spilling out as tiny insects; skyscrapers are long-necked monsters clawing at the sky; cars are shiny metal snails leaving slime trails on the road; and ships are bloated iron whales. Even the smog becomes a toxic octopus curling up to the clouds.
The speaker seems uneasy, even afraid. Words like "sly," "monstrous," "toxic" and "sterile" make the city feel cold, dirty and unnatural, and people look small and powerless beneath it. The final stanza pulls the idea together: the city is alive, hungry, and waiting to attack "like all wild animals do." The mood is menacing and claustrophobic, though the vivid, inventive images also show a fascination with this noisy, crowded world, as if the speaker can't look away from it.