In article , Ignoramus4371 wrote:
I want to glue a piece of steel to my truck's windshield, with some
threaded holes so I can attach anything to it (such as radar detector,
parking permits etc).

My question is, what sort of steel glues best

Clean, smooth, flat, and small (large pieces won't mate to the curvature of
the windshield -- you want something the size of a rearview mirror mounting
button).

and what is the right
surface prep. Should I sandpaper it? Should I sandpaper the glass?

No to both.

What is that rearview glue exactly?

Cyanoacrylate aka "superglue".

Also what is the minimum ambient temp at which I can do the gluing.

Consult the manufacturer of the glue. Typically 60F and up, I believe.