'Breastplates' in the Bible

They had breastplates like iron, and the noise of their wings was like the roar of chariots with many horses rushing into battle.

This was how I saw the horses in my vision: The riders wore breastplates that had the color of fire, sapphire, and sulfur. The heads of the horses were like lions' heads, and fire, smoke, and sulfur came out of their mouths.