In Buddhism can all we percieve / experience b used as teachers? ...I have been working on this one question for a while so can everything we experience in life internally and externally be used as our teachers from a Buddhist point of view?examples..
Anger = powerful emotion active in a person when one is threatened or insulted ,,an injustice over a issue etc also known to protect the persons personality ( possible to say anger is a friend then ! ) anger is an emotion that is automatically generated ,defense mechanism. It is repetitive and has been for x million yrs within the human psyche.  We could also say it  exists in lower beings birds ,goats , dogs etc so anger could be an important link to other forms of life by now I think you'll get some idea about just one state of mind that's revealed so much ...
The Buddha told us the three marks of existence, all things which exist in the mind have these properties:

Sabbe sankhara anicca
Sabbe sankhara dukkha
Sabbe dhamma anatta
All conditioned things are impermanent, All conditioned things are suffering, All things are without a self.

This means that everything has the potential to teach us. We can learn about impermanence, dukkha, and not-self from anything which arises in the mind.