A reader writes:
Something occurred to me, though. If you're armored all over, including gauntlets, how can you hold a sword?
Wouldn't covering your whole hand with metal make it really easy for the sword to just slip out, or twist so you're whacking people instead of cutting them? How did/does that work?
Gauntlets were, and are, not steel gloves. They cover the back of the hand and wrist, which is the part your enemy can actually hit, not the gripping surface on the inside. Sturdy gloves were usually standard equipment too; they went along with all of the other padding and covering that went under and over your armour, to help soak up the shock of impacts and stop your mail from ripping your nipples off.
There were many kinds of armour gauntlets, some of which probably had plates and/or mail permanently attached to a glove. And there may actually have been full-coverage metal gauntlets, for some reason, too; many odd kinds of armour have been made, and many of the most impressive pieces were for display or ceremonial purposes, and so didn't need to be practical.
(Whenever you start talking about this stuff you tend to end up with a giant comments-thread argument among a bunch of people who know an awful lot about historical weaponry, or think they do because they've read a lot of Dungeons and Dragons sourcebooks.)
But, in general, gauntlet armour was for the backs of the hands.
Today, most things called "gauntlets" are whole tough gloves - motorcycle gauntlets, welding gauntlets, et cetera. They'd probably work well as undergloves for armour.
(The abovementioned Nikolas Lloyd's site has a page about armour he's made, but he's only done mail and hoplite armour. But on the mail page he uses the term "preventing over-much beflapment", and that should be good enough for anyone.)