Describe the composition of a coin?

It's not clear what you're asking. Coins are normally composed of metal, sometimes mixed together as an alloy, sometimes in layers like US clad coinage, and sometimes in bimetallic coins with a center of one metal and an outer ring of another like Canadian $2 and EU €1 and €2 coins.

If you're asking specifically what metals coins are made of that's much more complicated to answer because it depends on the country that issued the coins, what denominations and often what year the coins were made. If so please post a new question with more specific details.