I'm wondering if anybody knows what kind of breeds it was that medievil knights used to ride into battle and for jousting etc. I figure that much be pretty big to cope with a full grown man in armour, with a weapon and saddle.

Why do you want to know? Are you entering a jousting tournament ;). I was curious about this as well so I did a Google search and two breeds that came up was the Friesian and the Destrier.

The breeds of Horses used depended on the country, and what was available to the soldiers at that point.

Naturally a Horse would have to be strong enough to support a man wearing heavy armor, but the sizes and breeds of the horse still did vary a good bit.

I want to know because a friend of mine wants to do a medieval-themed wedding, with the groom as a knight in shining armour, but they weren't sure what they should be looking for in a horse.

Ahh, I see. Definitely sounds like quite the wedding plan to me!

Hopefully it all works out, and I will try to do a little bit of research for you when I have a moment or two to spare.

As I said though, the breeds and sizes did vary a good bit though. As long as you are sure the horse is strong enough to support the groom in armor, it should work.

Friesians and Morgans seem to be two popular breeds for jousting these days. Any breed with a short strong back should work fine, although those with nice long manes and tails add a certain touch of romanticism to the picture. I've seen stables that rent horses for weddings, perhaps they can look around for someone who does that?