If you take a chunk of steel wool and run a 9V battery over it, it glows briefly, then stops burning.

However, if you spin the wool once it's alight, the oxygen being forced over it is sufficient to allow continued combustion.
As the wool burns, centrifugal force causes small pieces to fly off, leaving the trails when viewed via a long exposure shot.
If a chunk of burning wool escapes and hits a hard surface before it's burned out, the embers fly out, making 'spiders' of burning steel.
The images here are unedited apart from resizing and cropping to fit the page.