How to describe this metallic sound?

What about whipped?

the hum if the blade as it whipped through the air.

Try talking about the blade as a person, that may help?

Think about vibrations, the wobble of the blade, sparks, flashes of light from the sun.

Try to get across the ethereal nature of the sound so as to evoke the almost indescribable yet quite precise idea you want to convey. “So attuned is Hikaru to the deadly arts that he can foresee his opponent’s every move, so fluent in the unspoken and unwritten language of death is the veteran warrior that to him, her every breath speaks volumes, the crunch of the gravel ‘neath her feet a portent of what’s to come, the twitch of her lip, the beating of her heart, the dancing of the moonlight along the cool steel of her bloodthirsty blade sings to him a chorus, the soundless shriek of the wounded air, split by her sharpened steel, silences all of nature and awakens in Hikaru an ingrained instinct passed down through generations from father to son. The clash of their folded steel, to him a symphony an ancestral cry a warrior’s call, and will be the last thing she will ever hear.”