Which metals are most used on Earth?"

 The most commonly used metals on Earth are iron and aluminum. They are consumed in far greater quantities than any other metals.

Here's a breakdown of the most used metals and why they are so essential:

 * Iron (and Steel): Iron is the most used metal globally, primarily in the form of steel, which is an alloy of iron and carbon. Its popularity is due to a combination of high strength, durability, and relatively low cost. Steel is the backbone of modern infrastructure, used to build skyscrapers, bridges, vehicles, ships, and machinery.

 * Aluminum: Aluminum is the second most used metal. It is highly valued for being lightweight, corrosion-resistant, and easily recyclable. Its low density makes it a preferred material for the aerospace and automotive industries, as well as for packaging (e.g., cans and foils), and consumer electronics.

 * Copper: While used in smaller quantities than iron and aluminum, copper is a critical industrial metal. It is an excellent conductor of electricity and heat, making it essential for electrical wiring, electronics, power generation, and plumbing.