I'd advise you to not stop the medication without first consulting with your physician. Metoprolol is often the first line of medication offered for PAC's, PVC's, SVT, etc. I found it totally ineffective with any of these problems. It did however lower my BP, slow my cardiac rate, and made SVT episodes easier to convert. Also, the dose you are taking is small, so there is room to adjust. I "zombied out" at 200mg./day It felt like a cinder block was on my chest if I tried to do anything. I was fine at 100mg/day, and continue today at 75mg/day following my ablation.
Metoprolol, a beta blocker, us used primarily to help reduce high blood pressure. It also slows your pulse rate. The heart has to work less hard and that is probably why we feel the pacs pvcs less. I do not think it is designed to stop them. I would not stop taking them without first talking to your doc.