First of all, it's Yuusha Raideen.
This series is symbolic for Christanity in the Buddist country of Japan. The Devil Empire awakens after millenia of sleep and begin attacking human beings. Akira Hibiki, a descendant of the ancient Mu (Lemuria) Empire (Asia's Atlantis) is the only one who can fade into Raideen. The robot is semi-sentient and telepathically instructs Akira on how to operate it against the Devil's Dorome cannon fodder creatures and the Fossil Beast (magically created monsters) of the week.
In the first season, the Devils have captured Akira's father and turned them to stone. Only once a month can their heads become organic, and the Devils want Hibiki, Sr. to reveal the secret of Mutoron, the material that allows Raideen to repair itself.
In the second season, the Devils find Akira's mother and kidnap her.
The first season has Akira fighting the Devil prince Shyakin. In the end Shyakin makes himself into a giant Fossil Devil to fight Raideen one on one, and is defeated.
The second season, Baora (the head Devil) gains mobility and two of his generals compete on who will be able to face Raideen each week. The series took a bit more of a comedic tone at times in season two.
For classic anime, I recommend this series. It's dated, obviously, but you can see how we got to series and movies such as Gundam, Big O, and others now popular from watching this and others of the classics.
