“Is metoprolol used for arrhythmias?”

Yes, metoprolol can often help to control arrhythmias by blocking the action of adrenaline on the heart. But as it blocks other actions of adrenaline it can cause side-effects such as fatigue, breathlessness, faintness, poor circulation (cold hands and feet) and erectile dysfunction. Depending in what type of arrhythmia you have there may be better treatments, and some arrhythmias can be safely ignored.