The way I see it...
Fairy -> Dragon/Dark
>Dragons/Evil are the villains in fairy tales
Fairy -> Fighting
>Peace/Calmness in stead of violence and fighting
Steel -> Fairy
>Swords are often weapons in Fairy tales. Also, fairies exist in nature, far away from man made mechanization like steel.
Poison -> Fairy
>Poison is often the downfall/cause for strife in fairy tales, such as Snow White's poison apple and various evil potions, etc