Steel is a strong, highly versatile alloy composed primarily of iron and a small percentage of carbon (typically between 0.2% and 2.1% by weight). The addition of carbon hardens the iron, significantly increasing its tensile strength and resistance to fracturing. Here are its defining characteristics: Strength and Durability: It can withstand massive amounts of stress, weight, and impact, making it the foundational material for modern engineering and construction. Versatility: Steel can be rolled, forged, and machined into endless shapes, from massive structural I-beams to incredibly thin wires. Variability: By adding other elements, its properties can be altered. For example, adding chromium creates stainless steel (which resists rust and corrosion), while adding tungsten creates highly durable tool steel.