The amazing properties of metals have allowed us to use them to literally build the world we live in.  Their properties of ductility, malleability, high strength, luster and conductivity are what make them so useful.

Metals are usually crystalline solids. In most cases, they have a relatively simple crystal structure distinguished by a close packing of atoms. The diagram on the left shows the cations of the metal surrounded by a “sea” of rapidly moving electrons.  The electrons move freely about and because opposites attract, there is a very strong tendency for the atoms to stay in place.  However, because of the freedom of the electrons, the metal elements can slide past each other without causing cracking or fracturing of the whole crystal.

Here is a video that does a pretty good job of explaining this: Chemistry: What is a metal?

Metal crystal structure and specific metal properties are determined by metallic bonding – force, holding together the atoms of a metal. Each of the atoms of the metal contributes its valence electrons to the crystal lattice, forming an electron cloud or electron “gas”, surrounding positive metal ions. These free electrons belong to the whole metal crystal. (1)

• Ferrite: Relatively pure iron with tiny amounts of carbon that is soft and easy to shape. Gives iron its magnetic property.
• Cementite (iron carbide): Iron with much more carbon (and sometimes other elements) that is very hard and brittle. Essentially behaves like a ceramic material.
• Graphite: Pure carbon crystals, which make iron alloys hard and brittle.
• Pearlite: A mixture made of alternate layers of ferrite and cementite that looks like mother of pearl under a microscope (hence the name “pearlite”).
• Austenite: An alloy of iron and carbon present in steel heated to high temperatures.
• Martensite: Similar to ferrite but much harder.

Links:

• Video: What is metallic bonding?
• Primary Metallic Crystalline Structures
• Grain Structure of Metal
• Iron & Steel