Paper is much cheaper than metal. Hence, the cost of introducing and circulating new currencies in the market is very less as compared to metal coins. Carrying paper money is really convenient when compared to carrying metallic coins. Since paper is lighter than metal, you can carry more money with you wherever you go. Coins are easy to preserve and takes up less space and many times can be a profitable passionate hobby if handle with required knowledge.
Disadvantages of barter system:
Lack of double coincidence of wants.
Lack of a common measure of value.
Indivisibility of certain goods.
Difficulty in making deferred payments.
Difficulty in storing value.