To Be Hung
To Be Hooked, To Be Caught
intransitive verb, godan verb
Remember how 掛ける is "to hang something"? Well, 掛かる focuses on the fact that something is hanging, without specifying who did it. So it means to be hung. Use it to say a picture is hung on the wall, for example.
掛かる can also mean to be hooked, whether it's the picture hooked to the wall or a fish that happens to be caught on a hook.
These uses are all intransitive, so you don't need a direct object them. A hint for this is that 掛かる ends with okurigana that rhyme with ある, and those kinds of verbs tend to be intransitive.
The reading is the same as 掛ける, so as long as you know that you know this too.
時計をココに掛けたいんだけど、うまく掛かるかな。
I'd like to hang the clock here, but I'm not sure if it will hang right.
ポールハンガーには、男性のシルクハットが掛かっていた。
A man's silk hat was hung on a pole hanger.
ルーヴル美術館に行った時、モナリザが曲がって掛かっていた。
When I went to the Louvre, the Mona Lisa was hanging crooked.
お、魚が掛かったぞ！
Oh, fish got hooked!