Final answer:
Readers should visualize the freedom and playfulness in the metaphor of the characters being like wild horses and otters, to evoke emotional responses and vivid imagery.
Step-by-step explanation:
To connect to the metaphor in the excerpt from "Isaac and Casey," readers should visualize the freedom and playfulness of the characters likened to wild horses and otters. These metaphors suggest an uninhibited, joyful, and natural engagement with their environment, just as wild horses run freely and otters playfully interact with water. In literature, metaphors are intended to create vivid imagery and evoke emotional responses, allowing readers to further immerse themselves in the story by drawing parallels between the characters' experiences and the characteristics of the animals mentioned.