The four forces are lift, gravity, thrust and drag.
Lift opposes gravity.
Thrust opposes drag. Drag and weight are forces inherent in anything lifted from the earth and moved through the air. Thrust and lift are artificially created forces used to overcome the forces of nature and enable an airplane to fly. The engine and propeller combination is designed to produce thrust to overcome drag. Any inequality between lift and weight will result in the airplane entering a climb or descent.