I want to learn the metric system?

Here in the USA we use i have no idea what it's called but im tired of it. I think to learn it id have to froget about the old system and just bthink of the new one, but i cant seeing that i live here not there so how do you guys measure weight and everything are the pouns kilograms? and i got the tempeture stuff downn.. Why didnt we convert to the metric system?