The answer to this query is a bit drawn out, one gram of alcohol has 7 calories in it, but these calories have no nutritional value. They are basically what we call empty calories. High sugary foods like a lot of desserts also have them. So any calorie that you consume not giving any nutrition value is termed as empty calories.
But alcohol by itself does not mean you'll gain weight. Like, check out this study where two groups were taken with one group consuming about 4 beers a day compared to a matched group of non-drinkers. The result was that the drinkers consumed about 16% more calories than the non-drinkers. Both the groups also had an identical physical activity level. Now you would think that the drinkers put on some fat but the reality was both groups had the same body mass indexes despite the 16% extra empty calories the drinkers consumed.
Secondly, alcohol also lowers your inhibitors, meaning you are more likely to eat junk and pile on more pizza slices than you would ordinarily have. Add that with the increased appetite after alcohol and that might be a recipe for disaster if this habit persists.
But as we always do here, the broader goal is happy sustainability! And we aren't hypocrites here, our whole team also partakes in drinking on the weekend here. But we practise moderation to get that decent happy high but not to get overly drunk and regret it the next day. Because at the end of it drinking is harmful, but so is sitting in front of a computer for too long, not getting enough sunlight or staying up till late. So if a drink from time to time lets you release stress and gives you mental satisfaction, go for it, the pros outweigh the cons.
On a final note, always practise moderation while drinking and don't go overboard. Do not drink and drive no matter what. And fun fact, if you don't drink the whole week and think you can go all out and binge drink on a Saturday, that's actually worse than having a drink every day.