There are several variations in the use of helicopters for military purposes.
First, you have the logistics helicopters where some can certainly be called "heavy lifters".
They not only transport military personnel, but also a few vehicles or even an armored vehicle is no problem for a few!
Then, you have the so called "Multi Role" helicopters. They provide, for example, air support to the ground troops, transport the wounded or, especially in the coastal regions, carry out Search And Rescue assignments.
The "smallest" helicopters are the attack helicopters.