Hello and welcome to MedHelp and the Blood Pressure forum. Thanks for your question. Since you have begun a new medication and have a concern, it is best to call your doctor for advice. In the mean time, a normal pulse rate is between 60 and 100 beats per minute. You are just below normal, it seems.
Beta blockers will decrease your pulse rate. Do you know what your heart rate was prior to taking metoprolol? They do not recommend this medication for people who have a history of fainting from a slow heart rate prior to taking the medication. https://www.drugs.com/metoprolol.html You'll also notice from this information on the medication that it does have slow heart rate or pulse as a side effect. What is too low? Your range may be acceptable but you should verify this with your doctor. Let us know what they say.