Surely We have sent Our Messengers with Evidence, and We sent down with them the Book and the Balance to keep up mankind with Justice, and We sent down the Iron; in it has strong power and benefit for mankind, for Allah to know who will help Him and His Messengers unseeingly; indeed, Allah is the Powerful, the Exalted.
The Evidence, Book, Balance, and Justice mentioned in the verse is Adhikr. Mankind is bestowed with Iron, which is used for several purposes, including weapons of war, to test them on who will utilize it for helping Allah and His Messengers unseeingly, and who will utilize it for mischievous activities on earth. That means it is given to mankind for identifying who, by understanding the aim of life from Adhikr, is using it for forming the harmony of mankind as well as peace and tranquility among mankind, and who is using it for other purposes, such as robbery, theft, murder, bloodshed, terrorism, etc. Even though it is told in the verse to identify for Allah, who is the Three-Time Knower, it is actually for identifying for the believer who is the vicegerent of Allah. Such are helping Allah by utilizing Adhikr as the Balance and Trust to keep the universe in its equilibrium and propagating It to the entire mankind to utilize for that purpose. See explanation 9: 67-68; 14: 28-30; 49: 9; and 55: 7-9.