"It was a super tough race and I'm absolutely shattered. I feel a bit flat and I'm just looking forward to getting some rest," Malone said.
He had been fastest qualifier in 21.34s and that gave him the platform he needed for the final.
He's still to race in his No 1 event, the 400m, meaning Malone is potentially on course for a wonderful individual medal return across the three distances.
Malone, in the sport for just two years, credits his coach James Mortimer, who took charge and wrote a new programme for him last April.
"For the last eight months we've just been working on speed and it's gone from step to step."
He has been "working my arse off. All I do six days a week is train and read books. It's incredibly tiresome and boring, but it gets results."
Two more golds came in the pool, with Sophie Pascoe winning the 100m butterfly in her S10 single limb deficiency category, to give her a ninth Paralympic gold and become New Zealand's most successful Paralympian.
Cam Leslie repeated his performance of Beijing eight years ago and London in 2012, winning the 150 individual medley in the SM4 section in world record time. He eclipsed his own mark today.
Making of an Olympian: Cameron Leslie
Leslie qualified fastest in 2min 29.36s then smashed his own best mark by more than two seconds, clocking 2:23.12, heading home China's Zhipeng Jim and Denmark's Jonas Larsen. Leslie, from Whangarei, has dominated this event and was chuffed.
"I certainly felt a mixture of a lot of pain out there tonight, but I just had to get through the motions and remember the process. It is so easy for the wheels to fall off, if you focus on the pain," he said.
Nikita Howarth won her first medal in the 50m S7 butterfly, finishing third. She went in as fastest qualifier but clocked a fractionally slower 35.97s, five-tenths of a second behind silver medallist Courtney Jordan.
Paralympic debutant William Stedman of Christchurch set a Paralympic record of 5.35m on his first attempt in the long jump T36, before it was overtaken and he finished fifth.
The sailing trio of Rick Dodson, Andrew May and Chris Sharp sit second equal after the first day of five in their competition in the three-handed Sonar keelboat.