A few weeks ago I made the rookie mistake of washing the bike with soapy water, which is fine per se, but I also lightly washed the chain, big mistake. Obviously forgot to wipe it dry, then didn't touch the bike for some time because of sucky weather.
Surprise surprise! The chain started to get rusty. It got all dry and the chain links would get stuck on some of the front chainrings. Basically unrideable.
Fast forward to today, got myself some products (muc off drivetrain cleaner, wd-40 chain wet lube, parktool chain cleaner tool and solvent) and cleaned/lubed the chain the best I could
Results are pretty good I have to say, better than expected. The cassette is still a bit dirty but that's because I was out of clean cloth and out of time. Particularly pleased with the chain; even after washing and lubing it, some links were still stuck so had to move them about by hand until they got loosened up.
Lesson learned from today: buy plastic gloves