Iron is a specific type of metal, but the category of “metal” includes many other elements beyond iron. Iron is a single elemental substance, while the term “metal” refers to a broad classification of elements on the periodic table that share distinct physical and chemical characteristics. Understanding the difference between this general class and the specific element helps clarify why certain materials are referred to by either name.
What Defines a Metal
A metal is a classification applied to elements on the periodic table, typically found on the left side, distinguished by shared physical and chemical characteristics. These elements possess a characteristic metallic luster when polished. The most defining physical property of metals is their excellent thermal and electrical conductivity.
Metals generally exhibit high density, high melting points, and the ability to be shaped without breaking. This includes malleability (the capacity to be hammered into thin sheets) and ductility (the capacity to be drawn into thin wires). Chemically, metals are electropositive, meaning they tend to lose electrons easily to form positive ions. Elements like gold, copper, and aluminum meet these criteria.
Iron: A Specific Elemental Substance
Iron is a distinct chemical element represented by the symbol Fe. As a member of the transition metals, it possesses all the defining properties of the general metal class, such as conductivity and a silvery-gray luster in its pure state. Iron also exhibits unique properties that differentiate it from other metals, particularly its specific magnetic and reactive behavior.
Pure iron is notably soft and ductile, but it is highly susceptible to chemical reaction with oxygen and water, a process commonly known as rusting or oxidizing. Unlike some metals that form a protective surface layer, iron rust occupies more volume and flakes away, exposing fresh metal to continued corrosion. Furthermore, iron is a ferromagnetic material, meaning it can form permanent magnets or is strongly attracted to them.
Iron’s Role in Alloys and Categorization
The frequent confusion between “iron” and “metal” stems from the reality that pure elemental iron is rarely used in industrial and construction applications. Iron is nearly always combined with other elements to form an alloy, which is a substance composed of two or more elements, with at least one being a metal. The most common iron-based alloy is steel, which is primarily iron alloyed with a small percentage of carbon and often other elements.
This alloying process is done to enhance properties like strength, hardness, and corrosion resistance, creating materials such as carbon steel and stainless steel. Iron is so central to modern material science that it defines a major industrial classification: ferrous metals. A ferrous metal is defined as any metal or alloy that contains iron as its main constituent.
Ferrous metals include steel, cast iron, and wrought iron, collectively representing approximately 90% of all metal refined globally.
In contrast, non-ferrous metals, like aluminum, copper, and zinc, are those that do not contain iron as their primary component. Therefore, when people refer to “metal” in a construction or industrial context, they are often implicitly referring to a ferrous alloy like steel, which is an iron-based metal.