I've read the comments of others about being bitten by horses. And it's true that they can and will bite. However, it is not their nature generally to do so. They are prey animals and when threatened, their first instinct is to flee. If they can't avoid a "threatening situation" to them, they will defend themselves by being aggressive and bite or kick. A kick can be far more damaging than a bite. Biting is more of a disciplinary act for horses within a herd not a fighting posture.

I've had horses for at least 40 years and have never been bitten or kicked. If approaching an unknown horse, do it slowly with hand extended so that they can smell and inspect you. Always watch their ears. Its natural for them to be forward and following whatever is of interest to him at the time. If they are laid backwards and flat against his head, back off as this is a very aggressive posture. You don't want to pick a fight with an angry 1000+ lb horse.

Some horses have reputations for being mean and biting people around them. John Henry was a thoroughbred racehorse who is in the Racehorse Hall of Fame as one of the most winning horses of all time. He was a notoriously mean and aggressive and people feared being around him including handlers. However, he had a change of heart when he got older and when he was retired and sent to the Kentucky Horse Park, he was allowed to roam the grounds freely and interact with anyone who was interested with no aggressive behavior. There's a story here that I don't remember but I believe that he was the only horse they allowed to roam the grounds on his own.