Pokémon have always had various ways of evolving into new beasties, and Pokémon Sword and Shield are no different. One of these curious contenders is the unassuming Snom, which can be found primarily on the northern half of Route 8 - known as Steamdrift Way. Just keep an eye out for one wandering around in the grassy patches, and avoid the lightning-quick Sneasel.
Considering how high a level they already are when you catch one, you might have already guessed that they're not waiting for a certain level to evolve, rather you need to meet some special requirements.
You need to make your Snom have a high happiness level, which is achieved by playing with them at your campsite, feeding them curry, and also just keeping them in your party. Our recommendation is to just keep playing with your Snom lots at your campsite, it'll love you in no time.
Once your Snom is sufficiently cheery enough, you need to wait for night to fall in-game (alternatively you can just change the clock on your Switch in the system settings, we won't tell anyone), and then level it up one more time. This can be done by battling, using EXP or Rare Candy, as long as it goes up one level, it loves you lots, and it's nighttime, your Snom will evolve into a majestic Frosmoth.
One last bit of advice; Snom is notably underpowered in its moveset, and so when it finally becomes a Frosmoth is may still not have many moves at its disposal. Head on over to a Pokémon Centre and ask the bloke on the left to make it 'remember' a move. This can be done for free and as many times as you like, so give it Quiver Dance and thank us later.