There are chemical concerns depending on your metal finish so you should confirm with the metal roofing supplier.
Ice and water shield for metal roof.
These categories are regular and what s known as high temp i never really thought too much about the difference until a customer of mine had a problem with a black substance oozing out between the metal diamonds on his roof.
Hence it s name is ice and water shield.
If you have a metal roof you generally don t have that problem because even if you do get ice it s going to build up at the edge.
Many metal roofs are attached using screws where ice and water shield prefers smooth fasteners for the best seal.
Grace ice water shield is a versatile underlayment material that may be used on sloped roofs under mechanically attached roof coverings such as asphalt shingles slate tile cedar and standing seam metal in many climate and assembly conditions see limitations for additional information.
Ht specifically for use under metal roofing.
Grace ice water shield is supplied in 3 ft wide rolls of varying lengths.
Note that grace makes grace ice amp.
And also in southern climates it s put on the entire roof because even if the shingles blow off it keeps the water out.