You can also buy non penetrating mounts that use weights rather than screws to hold them in place.
Installing antenna on metal roof.
In order to take advantage of a metal roof as a ground plane you cannot elevate a quarter wave vertical high above a metal roof.
A metal roof discourages the transfer of signal by reflecting it away from you.
Whatever you do do not put holes in your roof to attach your antenna.
So you may want to put the mount on the ridge capping at the top of the roof.
Thankfully there are special indoor antennae which will circumvent this problem and help you watch tv despite having metal roofs.
Thus buildings with a metal roof or many metal components will face difficulty watching tv.
Tin roof mount where to place the mount.
But what if you have a metal roof.
In order to mount an antenna on your roof without damaging it you should attach the antenna to the gable the fascia or the chimney.
I always recommend mounting tv antennas as high as possible.