I crush the iron, yet flow like a stream, A cradle for rebellion, a teenager's dream. I am hard as a mountain, I roll with the beat, And I stand at the altar where heavy keys meet. What am I?

I am proof that washing machines have a favourite snack.

I have padded cups but hold no drink, I have a headband, but no hair to hold back. I sit on your ears to help you think, Or deliver the beats of a favorite track.

Strum my strings with gentle grace, Melodies dance in a wooden embrace. With frets that guide your nimble stride, In my voice, the stories abide.

This nut has a hard shell and if you crack it open you'll find it looks rather like a brain. Because of that it can occasionally be used as an insult, either comparing someone's brain to the size of this, or just calling them this directly. When eaten on its own it can have a controversial bitter taste, but has found some popularity as a vegan substitute for mince.