If youre wearing something metal, you go through a metal detector then surely you would hope it does show up - Whats the point otherwise?
My issue is the boneheads who watch 50 people in front of them go through and then:
Look puzzled when asked if they have a laptop
get out their laptops out of their wee tumi bag
remove their coats
find the liter of evian water in their bag from the previous flight
try to drink all the water but give up after 10 seconds
have an argument
go through
come back
remove their belt that sets off the detectors most times they travel
blah blah blah....