I saw this little guy in the lemon balm this morning. It's a soldier beetle, apparently of the Cantharis genus, possibly the species rustica.
Soldier beetles resemble fireflies but do not have light-producing organs. Their larvae are carnivorous, and the adults feed on nectar, pollen, or other, soft-bodied insects such as aphids. Soldier beetles are important pollinators of flowering plants and eat garden pests, so they are good to have around.
Last year I found a larva similar to soldier beetle larvae in this exact spot under the lemon balm. I wonder if it's the same individual?