(Psychological / emotional perspective)
We hold within us many of the answers to our own difficulties, but often in dreams need a down-to-earth, mundane symbol to trigger off our ability to work out solutions. When we experience ourselves as trapped, the key to freedom symbolizing what action we must take can often appear as if by magic.
The image of a simple key can indicate that the solution is easy.
An ornate key can suggest a more complex solution. When we cannot find a key in dreams we may have to wait until the time is right or circumstances are working in our favour.