There are many factors that affect metabolism.
Size - The heavier you are, the more calories you burn existing. Also moving at a heavier weight burns more calories than moving at a lower weight. So as you lose weight you'll burn less. Muscle mass uses more energy than fat mass so ultimately you want to try to retain as much muscle as possible.
Thermic Effect of Food (TEF) - The amount of calories it takes to digest the food you eat. Some foods have a higher TEF than others. Also eating more food will cause the calories burned by TEF to go up, and in the inverse, the TEF will go down when you eat less. There's not much that can be done about that but at the same time it's a very small contributing factor.
Non-exercise activity thermogenesis (NEAT) - The amount of calories you burn doing things that don't involve exercise. This tends to be the biggest factor with plateaus. Your body just subconsciously will stop doing things or do things less energetically to save energy. For example, I personally am a big fidgeter, but when I'm on a diet I will stop fidgeting. I'll eventually start walking slower. I become increasingly lazy and stop doing tasks or do them half-heartedly. Even small things will change like I've heard some people notice on video that their blinking slows down. These small changes when spread throughout a day will really add up.
Exercise activity - The amount of calories you burn doing exercise. Your performance, and thus energy expenditure, will go down as energy goes down.
What does all this mean?
The ultimate goal is to retain as much muscle mass while simultaneously keeping energy expenditure up. The first thing to do would be to go slow. A 1000 calorie a day deficit will surely eat up more muscle mass and cause you to crash faster. A slower, 250 to 500 calorie deficit will be much better.
Another effective strategy to this would be the "diet break". A diet break is basically where you eat at maintenance for a short amount of time. Though instead of two months off, you can do two weeks off. So you could, for example, eat at a 500 calorie deficit a day for two weeks, then eat at maintenance for two weeks. Then diet for two weeks and maintenance for two weeks. This will cause your NEAT and exercise performance to more-or-less stay the same. You may even regain muscle lost during the diet phase while in the maintenance phase. This will effectively double the length of your diet, so it may not be a good strategy if you're trying to make weight for some kind of competition.
You'll inevitably hit a plateau if you diet long enough. In which case, congratulations, you found your new maintenance. At this point, you can either drop calories even more, (shudder) increase cardio, or slowly increase calories. If you slowly increase by adding ~50-100 a week, then your NEAT will slowly but surely go back up. After a couple months you can try dieting again. So if you're eating at 1300 a day on your diet, increase to 1350 a day for a week. Then do 1400 a day for a week, then 1450, 1500, and so on. Once you're eating what you were prior to your diet (maybe slightly less since you would be smaller now), then you can restart.