The Quran's deliberate choice of 'muhl' for punishment and 'qitran' (molten copper) for constructive purposes (as with Dhul-Qarnayn's wall and Prophet Solomon's spring) creates a profound thematic contrast. It highlights that the same basic element (metal) can be a source of immense blessing and divine favor or a tool of severe punishment, depending on one's deeds and faith.

— Synthesis of interpretations from Al-Qurtubi and Ibn Kathir.

The description of the sky becoming 'like muhl' on the Day of Judgment is not just a visual metaphor but also a reflection of the inner state of the disbelievers. Just as their deeds were dark and foul, the very heavens will reflect this state of corruption and chaos, signifying a universe turned upside down by the denial of its Creator.

— Thematic synthesis based on the commentaries of Al-Tabari.