A monster is not the biggest truck that you can see in your lifetime, but is certainly more dangerous than a regular truck. It is made that way, so it can easily be driven over mountains. These trucks don't carry trailers like you see in an 8 wheeler truck or so on because it would be dangerous. However, it can be use to pulling some huge objects that can be attached at the back through the use of a chain. Though, it got a powerful motor, it might not be smart to use its full capability because of the danger of such action. You'll just endanger yourself while doing that.
Fortunately, you won't have to worry about that since this is just a game, but that doesn't mean that you don't need to be careful while driving. As already stated, you do need to drive it with safety in mind since the path that you would be driving on is a mountain path and things would be a bumpy ride. Try to grab as many flaming orb as you can because that would build up your score and this game is about points. However, if that would endanger your truck then just forget about it as you don't need it to get to the next level.