The image you've linked is a reconstruction of the Sutton Hoo burial, with a few elements borrowed from 7th century Vendel (Swedish) graves (the arm and leg armor). It's what abgreat man in the 7th century, with trade connections to Scandinavia, might wear. But not what you'd expect to see on a warlord from the late 5th century like King Arthur.

A historical King Arthur (who maybe did or didn't exist) would have worn a helmet and possibly mail, of a style similar to (and derrivative from) the armor of the late Roman empire.

We only have one surviving British helmet dating to the sixth century (and none from the late fifth), but it resembles styles of helmet being worn on the Continent during the same period. It's probable that something similar to this fourth century Roman helmet (scroll down to page 3) would have been worn, because surviving 7th and 8th century English helmets clearly evolved from the earlier style (suggesting someone was making derivative forms betwen the f4th and 7th centuries). You likely wouldn't see Arthur wearing something like the famous Sutton Hoo helmet, as that was based on a Swedish style and made several generations after Arthur was probably alive.

There's very little evidence that mail was worn in post-Roman Britain, but it's what Arthur would have worn if he could get his hands on some (probably either as a Roman heirloom, or from the Continent). It would likely have been a short-sleeved shirt that reached to his upper thighs. There's little evidence for forearm or leg armor from this period.

It's also possible that Arthur could have worn some kind of cloth armor, like that which was used further east. Or maybe rawhide lamellar (though we have no evidence for its use in Britain).

To what version are you referring to? The myth, Chretien de Troye's books, Thomas Malory's? There isn't one single Arthurian canon.