Understanding metaphor is a crucial element of learning another language. The cultural beliefs, context, and unspoken understanding wrapped up in metaphor can leave the foreigner totally lost. I remember being taught not only metaphors in Swahili but also the nature of not saying exactly what you're thinking. Taking a round-about way of saying something can be both more polite and an art form.
I love metaphors because the beauty of sharing an indescribable feeling with another person is a part of human existence I crave.
Here are some of my favorite mixed metaphors, uncredited (out of love for you, Mom):
"Do you follow where I'm coming from?"
(From "do you follow me? and "do you see where I'm coming from?"
"Button your seatbelts"
(From "fasten your seatbelts" and "button up your britches")
"You're blowing their trumpet?"
(From "blowing smoke up their ass" and "toot their own horn.")
"A heart as big as gold."
(From "a heart like a lion" or "a heart as big as Texas" and "good as gold.")
"Biting the hand that rocks the cradle"
(From "Don't bite the hand that feeds you" and "don't rock the boat" and maybe "robbing the cradle"
"It's like water under a ducks back."
(From "It's like water under a bridge", "It's like oil off a ducks back" and "below the belt.")