The Metro only existed because there is a demand for cheap, small, economical cars in other parts of the world, especially crowded world cities. Asia has a lot of these and Suzuki is a huge producer of the very smalll cars they buy. Indeed, they’re easily the biggest maker of ‘kei’ cars, a Japanese Govt. standard for very small, low-powered cars. In terms of Japanese sales, Suzuki is behind only Toyota, but the vast majority arr kei cars with meager profits. When they have tried to make bigger, nicer cars, like the Kizashi, they have been met with indifference and slow sales. Anway, the Metro was imported so GM would have a super small, cheap model to advertise and to help their CAFE. Same reason Ford brought in the Festiva/Aspire from Korea and GM sold the Aveo and Spark, rebranded Daewoos.
The Sonic is a more mainstream small hatchback, much roomier than the narrow Spark. If you want a tiny, simple car, your best bets are the Spark or the even tinier Scion IQ. I have a hard time recommending that one to anyone at all tall, and you might as well fold the back seat and forget about it. It’s not even useful for small children, as trying to wrestle a child seat back there isn’t realistic. The Mazda2 is also a very simple car, buy pleasant, well put together, and with just enough power to feel safe. Of the seriously cheap and small models it would be my choice. Or and Kia Rio or Hyundai Accent, though most seem more heavily optioned and pricier. The Honda Fit, likewise, but it is so much bigger and roomier it doesn’t feel like it belongs in the same class, though it is still a simple, inexpensively, economical car. Also exceptionally well made and the winner of just about every comparison test it has ever been a part of. I don’t like the interior much, but I understand the upcoming one is much better. If that’s true, and it’s a little better as a freeway cruiser, it will be hard to beat. It could fill the needs of probably half the car-buying population.