I am not sure could it be mint.

Or a weed...

are the leves scented?

Looks like a Lamium

Looks like a Nettle to me

It looks like Nepta Cataria (Cat Mint) to me.

Suppose you wait until it flowers and post another photo?

I smelled it and yes they do smell good. Tasted it, as well, and it has minty taste but not quite like mint. Has a lemony flavor along with it. Does catnip or cat mint have a mint flavor?

Not wise to taste any plant unless you know exactly what it is - you could end up with a stomach upset or much worse.

If it has a lemon flavour I think it might be Lemon Balm. Cat mint isn't edible and you would have every cat in the neighbourhood rolling in it.
Google images and put in lemon balm and compare the images to see if they are the same.

I think Lemon Balm as well, roll some leaves in your hand should smell of lemon, invasive

there is a lemon mint too.

In my experience lemon balm can fall over, but it doesn't get that curve in the stems - they're more rigid than this is.

It looks like Apple Mint (Mentha suaveolens), some varieties of which have a lemony or pineapple overtone.

If it is lemon balm it will look rather different after flowering. Instead of those lush green leaves there will be rather narrow ones on the old flowering stems and not much at the base of the plant. The flowers will be very small white ones. It makes a splendid tea, one spray is enough for two cups. It is soothing, calming and also good for fevers. It also seeds itself freely. Mint also makes an acceptable tea. It isn't catmint, whose leaves are more grey-blue than your photo.

As for tasting, I have seen mushroom experts identify by taste, being careful to spit out every last bit - not suggesting you should try it of course!

Just another thought - perhaps its hedge woundwort, in which case the flowers will be red, and the plant spread vigorously by underground runners. But I think the leaves are too bright green for that one.

Thank you, all. It is catnip. :)