(Shire mare & foal)
A heavy horse is a large horse bred to perform hard / heavy work such as ploughing and farm labour. The heavy horse is used today for shows, forestry work, leisure riding, driving, and some are still used for supplying breweries and on farms.
A Shire Horse (heavy horse) holds the world record for the biggest horse, he stood at 21.2 ½ hands high, his name was Samson. Heavy horses are mostly quite docile, they have upright shoulders, a short back with strong hindquarters and almost all have feathers.
The Belgium Draft horse (heavy horse) is supposedly the strongest of the heavy horses, it is also probably my favourite. Sadly the Belgium Draft is still used for meat in some parts of the world. None of these photographs are of a Belgium Draft.

(Suffolk Punch)
It is a common mistake that heavy horses are just modern destriers (Medieval war horses) but it is horses like the Friesian who were the destriers, although it is quite likely that the heavy horse has some medieval war horse in it. But I am not an expert on it anyway.
Oh and the part about what they did for us: heavy horses have helped with farm work for centuries, transporting goods, supplying breweries, they helped to build some of the most impressive buildings and they helped in our wars too. Over half a million heavy horses were used in World War 1 supporting the military effort.
Anyway I am just about finished boring you now but I thought it was quite interesting.
The photographs are from a heavy horse show.
(Shire horse)
Oh and I have soaked the bonfire with the hose pipe now all I can do is see if they have re-lit it tomorrow.