If you dream about the key, then it means you found the solution for some problem. If you cannot open something with your key, you are doing things the wrong way. If you have lost your keys, then it shows unexpected troubles. If you found the keys in a dream, then it signifies the joy you will have, because of the solution you will find. If you gave your keys to someone else, it means that there is a person you can rely on perfectly.
Read more about dreaming of Key in other dream meanings interpretations.