Well, at least he's providing the security team with fair warning. Those detectors are designed to react to the slightest hint of metal, so we guess he's going to set off the biggest alarm in the history of the airport!
Yes, we know the t-shirt is a reference to the type of music that this gentleman prefers to listen to. It's still a bit of an ironic choice to wear when you're walking through a security gate - and even more so if he really did accidentally set it off.