Help identify this plant.

It doesn't look like any of the herb seeds I planted. No idea what it is.

Is it lemon balm?

it definitely could be. can you get more of a close up?

It definitely has the mint-like leaves of lemon balm. My balm is more rounded with scalloped edges though. Crush some and if it smells lemony, that's probably it. It could be catnip too, which has it's own distinctive smell.

A close-up is needed for better identification, including the stem.

crushing and sniffing a leaf might help, too!

It certainly looks like my lemon balm, though mine tends to get leggy very quickly.  I planted mine in my “herb bed” (it is dominated by a shrubby rose so herbs get forced out quickly) and it disappeared there but appeared in my “orchard” 15 meters away, so it could have come from anywhere.

As said, check the leaf smell.  I believe all mints have a square stem and are all edible.  

The plant on the right doesn’t seem to have the scalloped leaf edge - do you think it’s different?

Looks like lemon balm to me. Keep an eye on it, it will take over just like mint.
I was able to click on the photo and see it enlarged (large enough to read you've got bee balm planted next to it)-- is that not working for other people?

worked fine for me, i just wanted a closer look!

Sorry ya'll I'll get a better pic when I can. Just been busy and the weather has been rainy, which I love.  I'll get a pic and crush some leaves, see what happens. :)