Here are descriptions and comparisons of the different types of refrigerant metering systems.
The metering device also has the job of making sure that there is enough refrigerant flowing to the evaporator to ensure that it is almost fully filled with saturated refrigerant, while protecting the compressor by preventing liquid refrigerant from returning to its intake. And that is a pretty tall order, considering all the variations in indoor and outdoor conditions that the system will see during its lifetime.