glue to auto metal floor

If the floor is clean, grease free and slightly roughed up, it will hold until the end of time. I assume this is the interior of an automobile. It should not get over 125 degrees on an interior surface. The adhesive should be fine for adhering insulation. If the heat source is from an exhaust pipe being too close to the floor you might also consider taking some thin aluminum sheet metal and attach it to the pipe with a small airgap between pipe and sheetmetal, also between sheetmetal and floor boards. This will partially block the infrared transmission of heat directly to your floorboard. Again, there must be air gaps on both sides of the aluminum.

No, this can not be used to glue insulation to a metal auto floor.