[Yuukigami]

I wouldn't recommend thinking of 持つんだ as a command. It literally means "it is the thing that (someone) carries". It is for explanation. Although in certain contexts it can seem like a command. Similar to how んじゃない in certain cases can indicate some sort of negative command. But think of it literally, これを持つんだ。"It is that (you) carry this" That can be taken as explanation or some sort of a command, or more like...I don't know what the right word for it is. lol I would just look at it as explanation because it makes sense either way, at least to me.

Similarly, something like 調子に乗ってんじゃないよ！Literally means something like "It isn't the thing that you are full of yourself!" (調子に乗る＝(lit.)To ride a tone, mood, manner(there are a ton of English translations for 調子).

It is a bit hard to understand but it is better to look at Japanese literally and avoid "pretty" English, it makes more sense after a while. Try to avoid English translations as a whole when it comes to Japanese.