"Assuredly We have sent Our Messengers with manifest truths, and We have sent down with them the Book and the Balance so that humankind may live by equity. And we have sent down iron, in which is stern might and benefits for humankind, so that God may mark out those who help God and His messengers, though they do not see Him. Surely God is All-Strong, All-Glorious with irresistible might."
Iron is perhaps the most important and necessary matter for technology. It is also our most elemental material, as it is the core of the earth. So, this verse may also be referring to the origins of the earth. In addition, iron is indispensably necessary to make weapons to fight in God's cause to uphold His Word, and to eradicate injustice.
From another point of view, this verse is very significant in assessing a sound society and government. The Messengers are the God-appointed leaders of humankind, who always guided them to the truth and led them in all aspects of life throughout human history. The Book is the compilation of knowledge, instructions, and laws essential to humankind's happiness in both worlds. The Balance is the criterion to attain what is right in belief, thinking, and action, and also to realize justice in human individual and social life. Iron symbolizes force or power in human social life. Without the Book, iron (force) destroys justice and brings about injustice. Without the Balance, iron misuses the Book according to its own benefits. Without iron, the Book and Balance are not sufficient to form a good society and government. Said Nursi remarks: "Principles of wisdom and laws of truth have no effect upon ordinary people unless the former are combined with the state's laws and the latter with power." (The Letters, "Seeds of the Truth," 2:306).
"The Quran: Annotated Interpretation in Modern English" - Ali Unal, pp. 1113