The destruction of Jerusalem is vividly compared to a blazing melting pot where the city's residents are trapped beneath an inescapable anger. Repeating this harsh imagery serves to emphasize the sheer severity of the decree and the intense suffering that is about to unfold [רד״ק, מצודת דוד]. While the gathering of the people might seem like a simple collection [רד״ק], it is actually a forced confinement. The inhabitants are pushed into a sealed space with no way out. Historically, this points to the people who remained in Jerusalem after the earlier exile of Jeconiah. They found themselves locked inside the city walls as if inside a furnace, completely unable to flee [מלבי״ם, מצודת דוד].
As the destruction unfolds, God breathes the fire of His fury upon the trapped population. This act of fanning the flames symbolizes how God constantly worsens and intensifies their suffering [מצודת דוד]. The specific type of anger unleashed is a sweeping, universal wrath that overtakes the entire nation. Unlike a targeted anger that strikes only the guilty, this overwhelming fury makes no distinction between the righteous and the wicked. Its tragic nature is to consume and harm the population as a whole [מלבי״ם].
The climax of this process is the melting itself. While God directly gathers the people and fans the flames, the actual melting is described as a natural consequence that happens on its own. Simply by being imprisoned within the burning city, the people dissolve and melt away from the intense heat. This powerful imagery captures the absolute ruin and total loss that struck the nation during the final exile of Zedekiah [מלבי״ם].