Final answer:
The metaphor suggests that the party attendees are drawn to the extravagant atmosphere but lack substance and purpose.
Step-by-step explanation:
The metaphor about the moths in the quote suggests that the people who attend Gatsby's party are drawn to the extravagant and glamorous atmosphere of the event but lack substance and purpose, just like moths are attracted to light but have no clear direction. The use of the metaphor highlights the fleeting and superficial nature of the relationships and interactions at the party. The constant movement of the moths mirrors the constant coming and going of the party attendees, emphasizing their temporary presence in Gatsby's world.