I have actually never heard of a metal harness, but there are harnesses made  for more exuberant dogs. I guess my bigger questions is, How does she even get the harness in her mouth? I know my Maggie would chew on hers if I leave it out where she can get it, but not when it is on. Note that I only use her harness when she is on a leash, so it is not on her all the time. What types of harnesses has she chewed through?