My friend is a phrase to refer to someone the speaker has a friendly relationship with. It can also address a person directly, to show warmth, solidarity, or mild formality. Tone can be sincere or ironic depending on context.
The most I can do for my friend is simply to be his friend. Henry David Thoreau
Empty your mind, be formless, shapeless - like water. Now you put water into a cup, it becomes the cup, you put water into a bottle, it becomes the bottle, you put it in a teapot, it becomes the teapot. Now water can flow or it can crash. Be water, my friend. Bruce Lee
My friend asked me if I wanted a frozen banana. I said 'No, but I want a regular banana later, so... yeah.' Mitch Hedberg
He is my friend that helps me, and not he that pities me. American Proverb
He is my friend who grinds at my mill. Spanish Proverb
I would rather have a dog my friend than enemy. German Proverb