The Book of Genesis recounts several stories that involve dreams: Jacob sees a ladder with angels ascending and descending, Joseph dreams of his ascension to power, Pharaoh's steward and baker dream of their separate fates, and Pharaoh dreams about years of plenty and famine.
All these dreams were messages from G‑d. In fact, dreams are the medium through which G‑d would often communicate to the prophets.
Rabbi Schneur Zalman of Liadi explains that meaningful dreams emanate from a very high spiritual level; a level that completely transcends this physical world and can therefore feature supernatural events that completely defy logic.
But does this mean that our dreams, too, are messages from G‑d? Should we be frightened by a dream that portends doom?