Moist and sunny.

Try shasta daisy in front of monarda. It likes moist, rich soil as well.

Maybe add 2 more plants (something that blooms in early summer & another that blooms in late spring) behind the monarda & daisy.

Then the daisy & monarda will grow up taller than what is done blooming. I read that in Doug Green's book about how to plan a garden for the seasonal blooms. It blew my mind to put the spring plants behind, but makes total sense. Mid summer & fall plants can be in front of the bed & cover the others.

What comes to mind for the earlier blooms:
daffodils & pansies - spring
serbian bellflower & early daylilies - early to mid summer

Be sure to bait for slugs since they love all these plants.

'Zagreb' coreopsis is a good companion plant. That's the one with the bright lemon-yellow flowers. It has a rounded shape with fine foliage and is very pretty with pink flowers. Mine is still blooming profusely in full sun. I just lightly deadhead the first blooms. It doesn't seem to mind being moist as long as it has good drainage.

'Rozanne' geranium is also pretty with pinks and will bloom till frost. It's a little sloppier at the front of a border, but it will weave and climb through whatever it's planted next to. I have it in front of a phlox that gets ugly at the base.

Great suggestions! Thank you so much for the help. I'm taking out an enormous Hardhack Spirea that overwhelms that particular space in an oval bed I made. It will go someplace more appropriate. I've got a Bridalwreath Spirea, some Kerria japonica, and a Pink Dawn Viburnum around and to the rear of that space which should take care of spring. I think the Monarda will be much more interesting for summer than the Hardhack. And your suggestions for late summer and fall will be great right in front. Thank you!