You will find many Pokémon in the wild area in Pokémon Sword and Shield. One useful Pokémon you can find is called Elgyem, it is Psychic-type, which is always useful when you are battling combat or other Psychic-type Pokémon.
You have the highest chance of finding it in these places in the wilderness:
- Bridge Field during normal weather and overcast with a 10 percent chance, and during thick fog with a 20 percent chance in overworlds
- Motostoke Riverbank in thick fog with a 30 percent chance, but won't see it in the overworlds
You have a handful of options at your disposal. Unfortunately, you may have to rely on strong fog weather, which you can't access until you've beaten the game. You beat the game by getting your coach into the Hall of Fame, not when you complete all eight gym badges. After that point, you must begin to bring the Heavy Mist to the world.
Despite being unlocked, it still takes several chances to randomly spawn into the Wild Area, not to mention a particular area in it. To keep it simple, you can go to your Switch's system settings and change the date to 06/01/2020. When you return to the game, you should change several areas of the map to Heavy Fog, giving you a better chance of spotting it.
If you just want the next evolution of the Pokémon, Beheeyem, you can find it at Lake of Outrage. You must have the Rotom Bicycle update to cross the water, but you get it before you beat the game. Thankfully, you can find it with normal weather at a fair chance, so you can breed the one you find and acquire Elgyem without having to rely on Heavy Mist.