I used to try & eradicate creeping charlie from our yard, but one spring, when nothing else was blooming, I saw our local bumblebees feeding on the purple flowers, & ever since I have regarded this plant as a useful addition. I don't know if monarchs will feed on creeping charlie, though.

Had "Fred" on Pinks(not sure correct name) just the other day. ( See "Hummingbird" post for picture,) it was a plant that was given to me last year, so unsure of name. Maybe a dianthus of some sort. He sure liked it, or getting his picture taken, cause even when he got scared away
( couldnt' stay still that long.) he didn't go far and came right back to the plant.

I've seen them on what I think is a honeysuckle bush, and a cluster of chives that I let flower.

I've seen them on flowers in my lawn (dandelions)! I am really trying to love this 'flower', maybe food for monarchs will help.