In this verse, God uses a metaphor of a rusty pot to symbolize the corruption and sinfulness of Jerusalem. The pot is described as being covered with scum, representing the wickedness that has accumulated over time. This imagery illustrates the deep-seated nature of sin and the need for thorough cleansing and purification. Through this vivid depiction, God conveys the severity of the judgment that will come upon Jerusalem for its persistent rebellion and unrepentant heart.