Iceland's currency is the Icelandic Crown. It is good to have some cash with you - especially when you plan to visit places in the outback. But still, credit cards are very common and can be used even for smaller amounts. Often you don't need your signature but your credit-card pin (e.g. at petrol stations). So please check your credit-card pin in the forefront of the trip. There are ATMs at the Airport. Use them to get your first 200 EUR in Icelandic Currency.