Dean is the hearth.
His love is the simmering of the spaghetti sauce that bubbles away in the Bunker's kitchen, while he pokes up the pleasant crackle of the wood in the den's winter blaze and laughs as Castiel sneezes over the shimmer of old book dust. Dean protects his family, his home, even the world, with the strength of the white-hot element that courses through him. When away from the Bunker, Cas is sure the sunlight plays with Dean's hair, just for him, just so he can see Dean's own halo and be reminded that home is not in a place but in the warmth of a person.
Dean is an explosion.
When cornered or frightened, when his loved ones are threatened, Dean will lash out; he explodes like gasoline poured onto an open fire. His wrath knows no bounds. He consumes all that is around him and leaves utter destruction and devastation in his wake. Cas has seen angels, demons, monsters, and entire buildings left in nothing more than smoldering piles of ash at Dean's angry, scared feet. Dean is frightening when he is a consuming fireball, but he is effective, fiercely protective, and so powerful that his shock wave can be felt for miles.
Dean is a fever.
Dean is only a fighter by nurture; he is a lover by nature. His language is physical, tactile; his mouth is used for kissing rather than talking. Every time Dean's hands slide across Cas' skin, he is sure he is going to burn away in a slow rolling fever. Hips bump and curve, hands grasp, lips moan, and temperatures soar higher and higher until, like a boiler finally blowing off pressure, they are sated. But only ever temporarily. Castiel possessed vast amounts of knowledge as an angel, but it was only after becoming human did he learn just how sweet a fever could burn.
And Dean is branded into his very soul.