And to Solomon (We made) the Wind (obedient): Its early morning (stride) was a month’s (journey), and its evening (stride) was a month’s (journey); and We made a Font of molten brass to flow for him; and there were Jinns that worked in front of him, by the leave of his Lord, and if any of them turned aside from our command, We made him taste of the Penalty of the Blazing Fire.
Some former commentators have taken this to mean that a spring from the earth had erupted for the Prophet Solomon (peace be upon him) from which molten copper flowed out instead of water. But another Interpretation of this verse can be that in the time of the Prophet Solomon (peace be upon him) the work of melting and molding copper for different uses was done on a very large scale and the same has been referred to here as the flowing of a spring of molten copper for him. (21:74) .
The subjection of satans has been explained in Surah Saba Ayats 12 and 13 34:12 . Incidentally, these verses of the Quran clearly show that the satans and jinns who worked for Prophet Solomon belonged to quite a different genus from human beings. Therefore, it is wrong to pervert the Quran to prove that they were human beings as some modernist commentators have tried to do. It is obvious from the wording of the Quran and the context in which the story of the jinns has been related, that they were not human beings. Had they been so this would have been no special favor to Solomon, because human beings had already built the gigantic monuments like the pyramids of Egypt.
Maududi, Abul Ala (2010). Tafhim ul Quran. https://www.englishtafsir.com/Quran/27/index.html