HM04 Strength Guide - Pokemon Fire Red & Leaf Green
HM04 Strength is one of the few HMs that is fairly easy to miss if you don't already know what to do to acquire it. Much like the HM03 Surf before it, HM04 is obtained in Fuchsia City from the Warden but you'll need to acquire an item from the Safari Zone first.
In the southwestern portion of Safari Zone you'll find Gold Teeth, it's found just east of the building where you get HM03 Surf. When you enter this screen of the Safari Zone from the north - you just go straight south to find the Gold Teeth. If you still need some guidance just check out my screen shot below.
Bring the false teeth back to the warden in Fuschia City (the building he's in is shown in the screen shot below) and hand him the teeth. He'll give you HM04 Strength as a reward. That's all there is to it!