A really common trope about Scottish people, and highlanders in particular, is that they tend to drink a lot. While the negative connotations of this sort of thing are decidedly inaccurate with all things having been considered and taken into account, highlanders are actually quite fond of having a few drinks on a regular basis and as a result of the fact that this is the case you would find all of them in bars once the sun goes down and they would probably stay there until the sun comes back up!
The main issue that you are going to face in a Highlands bar would be deciding what to drink. Most of the top rated bars in Highland have a really wide selection of drinks, and these are the kinds of things that you might not be able to find in other bars around the world. Hence, you should choose carefully. You can only have a limited number of drinks before things start getting out of hand, and you want to be able to enjoy yourself before a point comes where you are forced to go home at any given point in time.
You can ask the locals for drink suggestions if you are confused. Highlanders are notoriously friendly, and if you tell them that you are here from abroad then they might just want to pay for your drinks. Don’t refuse them if they offer, as this might be considered a little rude although highlanders are probably never going to hold it against you. Being part of a lively crowd can be great for you, and it’s partly why these bars have such a great reputation in the world.