A common misconception of metal straws is that they are dangerous and can pierce through the mouth into the brain.

I mean it depends on the diameter of the straw. If the straw is thin as a needle, i imagine it sure can. I mean it's only about the pressure, not the total amount of force. And pressure is force per area, so if the cross-section area of the straw is small, it will generate enormous pressure and that can surely pierce your skull.