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?”