Spoilery tip: There is one point where you will find lava in an area that is not the main chasm where the lava normally is. It's a small area. Fill up on energy, create a suspend point if you're nervous, and dive in! I'm not sure if you're at this point or not, but it seems the most likely tip. When I got to this point, I did it just to screw around, but I'm pretty sure it's what you're supposed to do. When you emerge, you'll find yourself in a new area with a couple Metroids, I think, and each fight will test your nerves since there is no way, to my knowledge, to refill your energy on the other side, at least not before the Metroid fights.
Good luck!