Body horror is a sub-genre of horror, that is all about the destruction, transformation, and degeneration of the body, as well as one of my favorite sub-genres. Here's three titles I hope you've all seen.
Cabin Fever 2002

The tale of five college friends who rent a cabin out in the woods, to have a nice little get-away, and instead catch a deadly flesh eating disease. Cabin Fever is Eli Roth's first movie, and a pretty solid entry, but it enters body horror with the disease it's self. The slow rotting process, that you watch these characters go through is pure hell.
The Fly 1986

The Fly is one of the many body horror movies that David Cronenberg has directed, I could
write, and plan to, an article all about his work in body horror, so I'm going to just keep it to this one. The tale of Seth Brundle's tragic transformation into a fly is one of the few movies that lets you feel bad for the villain. The transformation from Seth Brundle, to Brundlefly is one of the most terrifying examples of body horror today.
Society 1989

Society is Brian Yuzna's first movie behind the chair, and far from his last. Society is a mystery film, with a lot of WTF moments, and a body horror finale that blows you out of the water, almost out of no where.
I don't want to give too much away, but the body horror elements of Society are some of the strangest in the genre.