It is possible, but not something a reliable roofing contractor would recommend. You’ll want your metal roof to have a solid structure, correct insulation, and sufficient ventilation–but it may not have these essentials when there’s a moldering roof still installed beneath it. Having the old system torn off completely before installing your new metal roof remains the best option.
DIFFERENT TYPES OF METAL ROOFS?
For the purposes of this question, we are going to break down the types of metal roofing based on the roofing materials.