Vocal teachers for metal and rock?

I want to learn safe metal and rock vocal styles, and want someone qualified to make sure I'm doing it in a healthy way. Do you guys know of anyone in the city who teaches how to do them? I've searched on Google and asked around a bit, but haven't found any. Most vocal instructors I've had are afraid to go near these styles and refuse to teach them since it can be damaging if not done right, but I want to learn to do it (by someone qualified to teach it, of course).