In dreams, horses typically represent a move of God marked by significant power. They are incredibly strong and are highly perceptive. Depending on the color of the horse, that could give more details as to the nature of that movement. But nearly all the time, horses are used to represent unstoppable power being ushered in and having significant influence.
If the horse has a rider, that broadens the use of this metaphor just a bit more. This is usually a picture of a messenger, a watcher, a patrolman…someone on assignment. If it’s several horses with several riders, think more along the lines of an army.
In Zechariah Chapter 6, horses are pictured with chariots, as being instruments that patrol, watch, protect, and ultimately give rest. Chariots were not used for transporting goods, but for war.