The inline 3 cylinder engine only made 55 horsepower, but there were actually weaker engines available for those who really wanted great fuel efficiency. A 49 horsepower engine was put in the XFi model, a special line that was ultra fuel efficient. That car could get 58 mpg on the manual transmission model. That puts most modern cars, including most hybrids, in the dust.
Customers often complained about the weak engines. They wanted a small car that could go fast. GM tried to appease them, building models with 70 horsepower engines. These cars could only get 35 mpg. You have to remember that during this time gas prices tended to be very low, often hovering around $1 per gallon or less. That meant there was little demand for the little car that could go slowly for a very long way.
This car was sold as a 3 door hatchback, 2 door convertible, 5 door hatchback, and 4 door sedan (only in Canada). The 3 door hatchback was the most popular body choice, and also the cheapest.
The Metro might be best-known as the car driven by Ned Flanders on The Simpsons. Homer Simpson is running after Flanders in one episode, and Flanders laments that he can't get away because he's driving a Geo. Many owners have reported similar experiences (jk).
You can find plenty of these on the used car market. There are many listings on eBay, along with hundreds of parts listings. Be wary of models with high mileage, as the engines tended to become less efficient over time.