The metal sleeves are to shield the spark plug wire ends they are supposed to come off with the spark plug wires when you remove the spark plug wires. You need to make a strong hook to get to the bottom of the shield and pull it off or use a long needle nose pliers to remove them. The trick is when reattaching the spark plug wires after you replace the plugs is to use lots of dielectric grease on the porcelain of the spark plug body so the plug wire doesn't bond to the plug. I normally see this problem with cheaper spark plug wire sets. Once you wiggle and pull on them you stand a high risk of damaging the spark plug wires!
I have the same problem with my 98 dodge ram, there is a metal sleeve that is around the spark plug, there is no way they come off with the plug wire it is not he insulating part of the wire. The sleeves are frozen in place and it seems they are so tight to the hex of the plug that the socket cannot get around the plug hex.
I did use a flat screwdriver to try and see if there was junk down at the bottom, I did loosen a bunch of junk and used my compressor to blow it out but still not enough to get the socket on the plug
I tried twisting and moving the sleeve with a vise grip but it will not move, I sprayed some WD40 in at the plug to try to loosen it hopefully in the morning.
It took me 40 hrs to change plugs on mine! I believe the piece of weather stripping for hood by windshield was bad and allowing water to enter the engine compartment and expedite rust. It was so bad that I couldnt even see the part the socket goes on. I ended up using my phone to take pictures inside the metal sleeves and using a hammer and small screwdriver to chisel the rust out. Sockets would not fit down in the metal sleeve and ground the exterior of a socket to get down on plug once the rust was removed. I could not remove the sleeves either. In fact I tore 2 of them to shreds and ended up buying expensive fabric heat shields for those plug wires. If you can get the shields out I suggest putting a lube on them so you can possibly remove them in the future.