Iron sharpens iron, and one man sharpens another.
Figurative: “The iron furnace” is used metaphorically for affliction, chastisement (De 4:20; Eze 22:18-22). Iron is also employed figuratively to represent barrenness (De 28:23), slavery (“yoke of iron,” De 28:48), strength (“bars of iron,” Job 40:18), severity (“rod of iron,” Ps 2:9), captivity (Ps 107:10), obstinacy (“iron sinew,” Isa 48:4), fortitude (“iron pillar,” Jer 1:18), moral deterioration (Jer 6:28), political strength (Da 2:33), destructive power (“iron teeth,” Da 7:7); the certainty with which a real enemy will ever show his hatred is as the rust returning upon iron (Ecclesiasticus 12:10 the King James Version, the Revised Version (British and American) “brass”); great obstacles (“walls of iron,” 2 Macc 11:9). Source International Standard Bible Encyclopaedia
Perhaps Proverb 27:17 could mean that we should prevent one another from becoming rusted from lack of use. Allow an instrument of good use to sit around unused and whatever skills that produced good works become dull and degraded to the point of uselessness.
My good friend has reminded me of this verse and many were the time when I saw ourselves first as the hammer and then as the anvil, but never did I see ourselves as the sword. It was always a matter of give and take.
During a worldly source search for the first uses of iron it was said that the iron first extracted to form any tool came from meteorites. The imagination can place such items in the realm of a gift from the gods, little g. Rare and precious are words that come to mind.
We do not live in the world and we have to endure the fantasies of sinners who fail to believe and connect to the Word of God which is a gift from God the Father, rare and precious. It is easy to envision the words contained in Psalms and Proverbs in worldly terms because that is where we live. But it is not where we worship.