Brake Issue
 

I have been having some issues with my brakes lately so I took my car into the shop to get it checked out and apparently the brake pads were completely worn down. I was under the impression that a pin in the brake pads would cause a noise as notification when the brakes were getting low but i was quickly corrected by the service rep that is helping me saying that pins are not used in metallic brake pads. Can someone please educate me on the topic?