Canon 40mm is awesome. It is tiny, it is brutally sharp from wide open and it's cheap. It even focuses fast. Focal length is useful for pretty much everything and if you put all these together, you'll see it's something that will never let you down.
You point, it shoots. Simple as that. You will not be able to get away with using such a large aperture that everything apart from the subject blurs into nonexistence, no. You'll have to compose properly. It is absolutely awful to use a first because you can't be lazy and get away with it. You have to become a good photographer to use it to its near full. You have to move around. You have to see. You have to think and come up with ways to get rid of unwanted elements. And when you do it all, the results pay off for all the hard work. It rewards you generously.
Or you can bring your favorite zoom lens and zoom in and out until you are pleased.
Being a full frame user does not mean you only like hilarously large lenses with light gathering capabilities that would give Stephen Hawking a boner. 40/2.8 is one of the best walkaround lenses made by anyone, ever.
A very close contender is the Fuji 27/2.8. Sigma 30/2.8 would be up there too but it inspires no confidence at all, being something made of such cheap plastics.
To stay native MFT, the Panny 20 F/1.7 is one of these great lenses too.
Kind regards, Wim