Although there are many metals and alloys available, just a few metals make up a majority of what is found in a vehicle.
Any combination of metals melted together uniformly is considered an alloy. They are often created to have the qualities of two metals (but they are chemically more complex than that; not all qualities can be kept) or to reduce costs. A common example of an alloy is steel.
This soft metal is very conductive, and has gone up in price considerably over the years.
Iridium is a rare metal used in small amounts on the tip of high performance and/or long life spark plugs.
This metal is strong on its own, but is even stronger when combined with other metals to make steel.
Platinum is a semi-rare metal used in small amounts on the tip of spark plugs.
Steel is a strong metal made from other metals like iron. It is very common in modern automobiles.