What type of metal is the key made of for a 2003 GMC Sierra 1500?

they are brass , steel is magnetic and will rust , brass , copper , high grade stainless , aluminum etc. are non ferrous and not magnetic

Thank you for your time and help. My spare key (the last & only one that I had) was thrown into some weeds and kudzu vines by someone and a suggestion for finding it was to get a very big magnet and go around the general area which made us think... the key is not steel. Therefore, the only other thing I can think of is using my Aunt's metal detector which may or may not be of any help. As difficult as this key has been to find its about the only option I have. Is there any other way to get the truck going without having to go through those tick and Skeeter infested weeds again???!!!!????

Use the metal detector and it will work if you find the spot where you lost the key.

if the key was attached to a chain or ring of some type those are usually steel and are magnetic but if it's under high grass it may not pick it up , who knows what else you'll find with a detector