When a horse smiles at you, it is usually an indication that the animal is happy and content. Horses smile by curling their lips back to reveal their teeth, which can often appear almost human-like in its expression. They may also hold this position for several seconds or longer if they are feeling particularly relaxed and comfortable with you. It’s important to remember that horses don’t necessarily ‘smile’ as a way of showing affection or pleasure; rather, it's more likely that they are simply expressing satisfaction with the moment.