I vote for a busted vacuum modulator on the transmission
But then again I have no idea if a metro automatic trans uses a vacuum modulator but if it does then that is probably what is causing it. Transmission fluid doesn't smell like any other fluid when it burns. Antifreeze and oil are pretty easy to tell they are burning by the smell.
Easiest thing would be look for a vacuum line going from the engine to the transmission and check and see if there are traces of fluid in it. The modulator should be able to be changed without pulling the trans hopefully.
When the car doesn't want to shift, if you hold it to the floor will it shift at the wide open throttle shift points fine or will it just hit the rev limiter and not actually go up into another gear?