"In 1987, more than forty years after World War II, the "Choujinki", an ill-fated ultimate weapon built in the final stages of the war, but never deployed, is put into action as the only hope in the battle against the merchants of darkness working in the shadows of peace and their frontline troops the Neros Empire. This is a record of Choujinki, a weapon that gave its power and limited life, not to the cause of mass death and destruction, but to peace."
—Plot summary from the DVD release.
Chōjinki Metalder ("Superhuman-Machine Metalder") was the sixth entry in Toei's "Metal Heroes" franchise, which aired in 1987 (lasting 39 episodes and a movie). Essentially a Spiritual Successor to Kikaider.
In 1945, at the end of World War II, Professor Ryūichirō Kōga was forced into creating a super weapon for the Japanese Imperial Army. Patterning his creation to resemble his dead son Tatsuo, Professor Kōga placed his cyborg into suspended animation because of his pacifist leanings against war.
42 years later, Professor Kōga's former assistant Kunio Muraki, now posing as a wealthy philanthropist named Kirihara Gōzō, has used a combination of science and alchemy to prolong his existence and to eventually attempt to raise Japan as a military nation again under his control as God Neros. Kōga decides to activate Metalder again to combat the menace.
Instilled with pacifist directives, Metalder is unable to combat the threat until Kōga allows himself to be killed by the Neros Empire, which drives Metalder to seek a path of vengeance. Conflicted by both his desire for justice and his peaceful ways, Metalder, under the new "human" guise of Ryūsei Tsurugi, attempts to find a balance in his artificial life while battling the forces of evil.
Metalder was one of the series that Saban used to create VR Troopers
- Acting for Two
- A God Am I: God Neros obviously.
- Armies Are Evil: Neros Empire's many sublegions.
- Artificial Human
- Awesome McCoolname: Ryūsei Tsurugi, the name of Metalder's human guise, literally means "Shooting Star Sword".
- Badass Automaton: Metalder just gets more and more badass as the series progress.
- Big Bad: God Neros
- Bittersweet Ending: Metalder wins the final battle against God Neros, but loses the ability to transform into his human form Tsurugi, keeping him in his cyborg form forever...
- Berserk Button: Ryūsei Tsurugi When he gets angry he can transform himself as Metalder.
- Bodyguard Babes: Secretary K and S to Gozo Kirihara.
- Body Double: Coolgin turns out to be dead-ringer for Kirihara under his mask. They eventually trade places when Coolgin disguises himself as God Neros while the real God Neros escapes wearing Coolgin's armor.
- Brought to You by The Letter "S": Metalder has a giant "M" below his waist.
- By the Power of Greyskull: IKARU! 
- Cool Bike: Metalder's Side-Phantom.
- Cool Car: Metalder's Metal-Charger is a Mazda Familia with the ability to transform into a Flying Car.
- Chuck Cunningham Syndrome: Mukimukiman and Fufuchu disappear from the rest of the series after #8. Given that they were a pair of goofy wrestlers in an army of cyborgs, mutants and armored warriors made them stick out like a sore thumb, which is part of the reason why they were quietly removed from the show.
- Co-Dragons: Coolgin, Doranga, Balsky, and Geldring; each of them is in charge of a different division of Neros Army.
- Curb Stomp Battle: Coolgin managed to defeat Metalder with a single slash in their first battle.
- Cute Monster Girl: Wisdom
- Darker and Edgier: the reason this show was cancelled, its much darker and grim tone turn away young viewers while teens and adults enjoyed it. it remains the darkest Metal Heroes show in the franchise.
- Defeat Means Friendship: Topgunder.
- Dogged Nice Guy: Hakkō to Mai.
- Dumb Muscle: Mukimukiman and Fufuchu.
- Expy: Besides Metalder himself, Top Gunder is meant to be a friendlier version of Kikaider's rival Hakaider.
- Four Is Death: The number of divisions the Neros Army has.
- Grievous Harm with a Body/Deliberate Injury Gambit: In Episode 18, Zargen (a member of Neros' Combat Robot unit) stabs Metalder in the shoulder with a magnetized knife, intending to blow himself up with Metalder in a suicide bomb attack. Metalder drives the blade down to sever his arm, then he picks up his own arm and throws it at Zargen as his Finishing Move.
- Heel Face Turn: Topgunder fights with Metalder but later becomes an ally of his. Also Wisdom and her son Hedogross Jr., Ben K., and Rhapsody, all join Metalder's side after fighting the first time.
- Homage: Metalder has more than a passing resemblance to Kikaider.
- Home Base: The Silver Carcass, an underground military base constructed by the Imperial Army hidden within the mountains. Its where Metalder gets repaired after battle and where he keeps his vehicles.
- Hitman with a Heart: Top Gunder becomes one after joining Metalder's side.
- Hot Scoop: Mai
- I Have Many Names: God Neros, also known as Kirihara Gozo, formerly Muraki Kunio.
- Legacy Character: After the original Wogger is killed, another of Neros' minions inherits his name and armor.
- Master Swordsman: Coolgin, who manage to defeat Metalder with one slash in their first battle.
- Instant Expert: Averted hard. Metalder starts out not knowing how to fight, and is injured in almost every episode early on.
- Love Triangle: Hakkō likes Mai, but Mai likes Ryūsei.
- Martial Pacifist
- Monster of the Week: Almost all of the villains are already shown in the Ghost Bank during the very first episode, though they're gradually eliminated throughout the course of the series as Metalder fights them or they fight each other.
- The Movie: Ryūsei goes to a temple and learns a martial art technique in order to defeat the Tag brothers. While the movie doesn't exactly fit in into the TV series' continuity (Ryūsei speaks with his alter-ego's voice for once), it does provide Fan Service by having Mai Ōgi in a pink swimsuit.
- My Death Is Just the Beginning: Professor Kōga.
- "On the Next Episode of..." Catchphrase: Koitsu wa Sugoize! ("He's amazing!")
- Power Copying: Balsky, the Commander of Robotic Soldiers division, gains the ability to transform into any of his fallen subordinates during his final battle with Metalder in episode 38.
- Power Makes Your Voice Deep: Unlike most toku heroes, Metalder was voiced by a different actor than the one who played his alter-ego Tsurugi.
- Rank Inflation: The Neros Army has a ranking system with ten classifications. Each division is led by a commanding officer with the title of Gaisei (Victorious Saint), while the next nine ranks below it goes from Gōshō ("Mighty General", the second highest rank) to Gekitōshi ("Light Fighter", the lowest rank).
- Robotic Reveal: Metalder sometimes when he got badly injured you can see his internal systems in every episode,
- Sexy Secretary: K and S.
- Soap Opera Rapid Aging Syndrome: Hedogross Jr. goes from conception, to birth, to adulthood, in a span of no more than 15 episodes.
- Spiritual Successor: To Kikaider.
- Supervillain Lair: The Ghost Bank, which is located in the basement of the Kirihara Konzern's main headquarters.
- Transformation Sequence
- Villain Song: The Four Armies of Neros
- World War II: Metalder was originally a weapon of Imperial Japan, but his pacifist creator refused for it to be used for war.
- Worthy Opponent: Top Gunder before his Heel Face Turn. Coolgin also considers Metalder this.
- "Rage!" or "Anger!"