Since 1st February 2008 Euro is main currency on Malta. Nevertheless, if you arrive with any world exchangeable currency, you could be sure; your money will be exchanged. Many hotels or restaurants even accept foreign currencies. There is 24 hours a day exchange bureau on the Malta International Airport and plenty of them all over the islands. It is recommended to change your currency to Euro. If you do not pay by Euro, you can be charged with some conversion charge. You can also find many ATMs in Malta – exchanging the money is not a problem there.
These are pictures of unique Maltese Euro coins.
In summer you can visit most of the banks during work week until afternoon. Most of the banks is also opened in the morning on Saturdays. Do not forget that banks are mostly not open on holidays.
If you got used to pay by card it will not be problem. Most of the cards accepted worldwide will be accepted in Malta as well (Visa, Mastercard…)