"Long snakes are very scary."

Translation: 긴 뱀은 아주 무서워요.

[GerardoFig2207]

Difference betwee 무서워 and 무서워해

[Staszek456]

무섭다 - to be scary
무서워하다 - to be afraid of

뱀은 무섭습니다 - Snakes are scary
나는 뱀을 무서워합니다 - I am afraid of snakes

It is however important to remember that in less formal speech, 무섭다 can also mean "to be afraid". For example: 난 무서워 - I am afraid.
It works just the same way as words 좋다 and 좋아하다. Even though the former means "to be good" and the latter: "to like", it is very natural to say something like: 나는 사과가 좋아 - I like apples.

And remember to always use proper grammatical particles!
나는 개가/뱀이/괴물이 무섭다.
나는 개를/뱀을/괴물을 무서워하다.

[cactuscoffeerose]

Unsure why it's not the 3rd person form of scary here?

[josueetcom]

There is not really a 3rd person form of scary. You're probably confused between the following

무섭다 - to be scary

무서워하다 - to be scared/afraid

The thing is, when there's both a topic and a subject, A는 B가 무섭다 (literally "with respect to A, B is scary") means "A is afraid of B" since the topic limits to who B is scary.

[SUGA_MY_LOVE]

Hobi be like, "I told you"