Chemotherapy uses chemicals that kill rapidly dividing cells in your body. Cancer cells are normal cells which have mutated, and one of their characteristics is that once mutated, they divide faster than normal cells. Hence, chemotherapies can be effective at killing them. However, chemotherapies generally are not targeted specifically at cancer cells—they will kill other rapidly dividing cells in your body as well. These include hair (which is why many cancer patients temporarily lose their hair), bones (which is why doctors need to be more careful with chemotherapy given to children), and more.
There are a number of chemotherapies that are used in melanoma treatment. In some cases they are used on their own, and in other cases they are combined together, or combined with other therapies (such as biotherapies). The following are examples of chemotherapies used in fighting melanoma: