Allah taught Dawud (David) to make coats of mail, or protective armor. The Quran states this in 21:80, describing the craft as a skill taught to him so that it could protect people in battle.
The subject appears again in 34:10–11, where Allah softens iron for Dawud and instructs him to make armor with carefully measured links. Islamic interpretation therefore treats Dawud’s metalworking ability as a divine gift, while also presenting him as a prophet, king, judge, and recipient of the Zabur, or Psalms.
A coat of mail is not the same as a solid metal plate cuirass. It is armor made from linked metal rings, flexible enough to allow movement while reducing vulnerability to weapons. Sulayman, one of the wrong options, was Dawud’s prophetic son and successor, but the Quran assigns this particular armor-making lesson to Dawud.