Changing Spark Plugs on 2005 GMC Yukon XL Denali

There appears to be a metal collar around the boot of the spark plug wire. How does one remove the boot from the plug in order to change the plug? Does this collar need to come off first?

Asked by for the 2005 GMC Yukon XL Denali
The metal collar on the spark plug boots on your 2005 GMC Yukon comes off with the spark plug wire. It is no simple task to get the plug wires of after 100k of driving. The best option is to try twisting the boot to break the seal between the plug wire and the spark plug. It is my recommendation that the spark plug wires be changed along with the plugs at 100k miles. It is to easy to unknowingly damage a spark plug wire when attempting to remove it after 100k miles of driving.
What's the purpose of these metal collars, then?
it is a heat shield
it is a heat shield