hmmm I has planning on putting down some plywood then metal panels on top wonder if that would be overkill. I live where it snows so wanted to have some layers of insulation to protect from the elements
In some places that's unnecessary and in some places it's a good idea.
We installed our metal on purlins, which is the usual practice in our climate. But in some places that are cold and humid you can get condensation forming on the underside of the roof and dripping into the coop.
Try to find out what local metal roof suppliers recommend for farm buildings/livestock shelters. They'll know your local conditions.