When you call on someone who is wearing a (usually
metal) band t-
shirt.
The phrase is used to express either anger or agitation towards a particular person wearing a band t-
shirt, thinking that they don’t deserve the t-shirt as they don’t listen to that band.
Today I saw a boy with a
Metallica t-shirt, so I came up to him and asked him to name 3 songs by
Metallica, and guess what? He replied “Isn’t
Metallica a clothing brand?”