Looks like leaf footed nymphs

I would consider those a bad bug, but are you wanting to attract monarchs to your milkweed? If so, I wouldn't use any pesticides in an effort to not harm the monarchs.

While they do look like the nymphs of leaf-footed bugs, since they are on milkweeds, I think they probably are the similar-looking nymphs of milkweed bugs. So, in this case, they are bad because they will destroy the plants you're growing for monarchs.

I'd either handpick them and drop them in a bucket of soapy water to drown or vacuum them off the plants with a Shop-Vac. A general way to tell good bugs from bad bugs is that beneficial insects usually are found in small numbers. Based on my experience over many years, whenever I see that many of any sort of insect all together in one place, they're not beneficial insects, other than if I come across a hive of bees.

Here's some info about milkweed bugs:

Milkweed Bugs