At the same time I can be low or high, I can be found where the ground meets the sky.
Mountains can be seen on the horizon; some of them are low (usually older mountains, which have eroded), some high (usually younger ones)
I may have a bald spot on top of my head, But pick a fight with me and you may be dead.
Snow-capped peaks are something you see on mountains high enough - these resemble a "bald spot" on the top of someone's head. But people who climb mountains—seen as a challenge or fight—could "lose the fight" often die.
Slow moving, slow growing, I eventually change, But I'll always have friends out on the range.
Mountains change very slowly, from parts of the earth moving as well as erosion; mountains are found in "ranges", that is, a bunch of them all together.