Most visits to Montenegro are trouble-free.
There is an underlying threat from terrorism. See Terrorism
You must register with local police within 24 hours of your arrival in Montenegro.
You must carry your passport with you at all times for identification purposes. Keep a photocopy in a safe place.
If you’re abroad and you need emergency help from the UK government, contact the nearest British embassy, consulate or high commission.
Take out comprehensive travel and medical insurance before you travel.
Source Article from https://www.gov.uk/foreign-travel-advice/montenegro