Like mountains, deserts in Into the Wild function primarily as means for Christopher McCandless to challenge himself, and as such, they illustrate his hubris. Not only does he fear the desert insufficiently; he behaves as though it has been put there purely in order to test his competence.
Presumably named by McCandless after a song by British rock band The Who, the bus stands for the good fortune he repeatedly encounters in his odyssey through the American West. After all, what are the odds when McCandless forges into the bush that an abandoned bus will be waiting there for him to live inside? Of course, McCandless dies inside the bus, too, indicating that his luck has run out.
The moose that McCandless shoots and then, heartbreakingly, fails to preserve stands for his relationship to the wild in general. Moose meat could prevent McCandless from starving to death. Because of his hubris, however, he has not prepared adequately for the enormous task of curing the flesh and ultimately fails at it. The consequences are fatal.
In Into the Wild, mountains function not as scenery, nor are they especially significant geologically or historically. Instead, a mountain is an obstacle to be conquered, a way of testing one's capability and character, especially in the chapters of the book where author Krakauer recalls his own youth.
Many rivers run through Into the Wild. Like deserts and mountains, they test Christopher McCandless's survival skills. Unlike other natural formations, it is a river that defeats McCandless and kills him. Because he has not predicted that the river separating the "Magic Bus" from civilization will swell with snow-melt, he cannot cross it in late summer, when he intends to leave the woods. And because he (intentionally) lacks a map, McCandless is unaware of options for fording the raging waters.
The yellow Datsun is emblematic of Christopher McCandless's genuine disinterest in material things. Americans value their cars. McCandless leaves his in the desert.