The metal has to be grounded, many people think touching their cases will remove static, but unless its still plugged in.(which contrary to popular misbelief is not a bad idea) the charge will not ground, and you will still have static charge.
Lesson, always work on your pc with the psu plugged in.
"The Cash Left In My Pocket,The BEST Benchmark"
No Overclock+stock hsf=GOOD!