Why grinders are not recommended to cut roof sheets

There are many ways to cut roof sheeting. Most roofers use various power tools in lieu of the traditional tin snips.
But there is one tool that should never be used to cut a roof sheet - and this is a grinder. The hot cut from a grinder destroys the ability of the protective coating on the roof sheet to mend the fresh cut and protect it from rusting.
Most roofers do not see the long term repercussions of grinder cutting because they do not re-visit old roofs.
You can see result of hot cutting on this video.

[@billikonomou1542]

any good roofers in melbourne you may recommend cheers

[@roofingportal]

Sorry Bill,
We have not had the time to put Melbourne roofers to the test yet.