1. Flies symbolize dirtiness, decline, destruction. They indicate that all your efforts at the moment are futile and the plans you're making won't be realized..
2. Flies that fly around you in a dream may be a sinister portent of a severe contagious disease..
3. An annoying fly in the room may mean that an unpleasant person will try to enter your home..
4. If in a dream you're squashing or killing flies, this means you'll handle the troubles that will rise before you..