Horses cannot converse with us with their voices so they do so with body language. Here are a few tips in reading your horse
A horse's facial expressions can be very telling. A horse that is annoyed will screw its nose up in disgust much like we do! A horse that is worried about something may have wrinkles around their eyes, much the way we look when we are worried. Anxious horses are often tight-mouthed. Horses that are aggressive usually have wide open eyes and stare fixedly at the object of their aggression. When horses bare their teeth it is a threat that the horse is going to bite. A horse that is feeling submissive will often back away and avoid eye contact with the other horse. These signs may be difficult to read at first, but the more time you spend with your horse you'll find reading him becomes easy.
The ears on a horse are their most expressive body part. It is often easier to tell what they are feeling through their ears than any other body part. Angry or aggressive horses will pin their ears straight back while stretching their heads forward slightly. Horses that have their ears pointed forward are interested in what's before them, but are likely not paying attention to their rider. Floppy ears tend to indicate a horse that is relaxed. Ears that are flickering back and forth indicate a horse that is both attentive and listening to their rider.
A few emotions can be read by watching a horse's tail. Excited or aggressive horses hold their tails up high. Horses that are scared or frightened often place their tail tight between their legs. Swishing their tails up or down or side to side can indicate annoyance, such as when flies are biting them, or pain such as when they are colicing.
Your horse is communicating you just have to learn to listen with your eyes!