Chojinki Metalder (超人機メタルダー,Chōjinki Metarudā?, Superhuman-Machine Metalder) is the sixth and shortest entry of the Metal Hero Series, running from March 16, 1987, to January 17, 1988, for only 39 episodes. Toei went for a darker and more grim direction for Choujinki Metalder, and this turned off younger viewers. As a result, ratings started to slip in the second half, and the series was cancelled after just 39 episodes, making it the shortest Metal Hero series.
Originally, the action footage of Metalder was going to be adapted for the unpiloted show, Cybertron, starring Jason David Frank from Mighty Morphin Power Rangers but was then canceled. Later, they reused the same footage for the first season of VR Troopers.
For distribution purposes, Toei refers to this television series as Metalder. On February 21, 2007, Toei released the complete Metalder TV series and film on a seven-disc DVD set.
In 1945, Dr. Ryuichiro Koga designed Metalder as a top-secret weapon for the Japanese Imperial Army for use in the Pacific War, modeling it after his late son, Second Sub-lieutenant Tatsuo Koga. However, the pacifistic Dr. Koga put Metalder to sleep in the Silver Carcass base and left for America to work for NASA. During the 42 years, Dr. Koga's former colleague Major Muraki became the evil God Neros, ruler of Neros Empire. God Neros sends out his massive armies to kill Dr. Koga, who learned of their organization and returned to Japan to activate Metalder. Koga desperately tries to activate his android creation, who he named Ryusei Tsurugi, but the android is unable to understand what to do. In order to give Ryusei a "purpose", Koga runs out of the Silver Carcass base, allowing Neros' troops to kill him. Suddenly seeing his creator die, Ryusei becomes shocked, and soon is beaten by Neros' troops. Ryusei becomes fueled with rage, evoking the conversion to his 'true' form, the android known as Metalder. After a brief battle with Coolgin (which he loses), Ryusei goes onward, meeting future friend Mai Ogi.
Both Metalder and Kamen Rider Black were the heroes that don't have their own weapons in their disposal and rely only on physical attacks.
In the French dub of Choujinki Metalder, the entire music score by Seiji Yokoyama were replaced with their own musical pieces by Shuki Levy himself, who was also worked with Saban Brands. However, Episode 17 and 18 kept the saxophone variant of the original Metalder theme song.