Interesting! I interpreted the sentence as referring to the metro system as a whole rather than a specific train, and that could be a slight cultural thing?
I think most English speakers say we're "in" a car (or other small vehicle), "on" a train/bus/boat (but "in" a carriage/seat/berth), and when it comes to talking about a rail system, or tunnel network, at least in Britain, we're "on" xyz line, but "in" the system.
e.g. "Me mobile reception's goin', Mum: I'm in the Tube, about to go on the Northern. It's really crowded!" (Tube = London Underground; Northern Line: has some of the oldest and deepest tunnels -- think they've fixed the reception issue since I was last there, though! =p)
Greetje548205, Thank you. To further lend or help enhance my grasp of finnish thought (sami?) behind its structural diction/grammar, I'd appreciate your highlighting, whether literally translating olla with partitive adjective OR adverbialAdj would permit inferring something like: • "It is with a crowd in/on the metro" OR • "it is with crowdedness in/on the metro" ?
Not very big difference. The former is common language and sounds like a normal everyday thing, like a lot of people coming and going. The latter, whereas, has hints that something unusual is happening and there's something about the people that are crowding the metro (e.g. taking shelter).