"Full Metal Panic!" is a science fiction mecha anime series that blends military action, comedy, and drama. The story is set in a world where advanced technology, particularly humanoid combat robots known as Arm Slaves, plays a central role in global conflicts. The narrative revolves around Sousuke Sagara, a young and highly skilled soldier from the covert anti-terrorist organization Mithril. Sousuke is assigned to protect Kaname Chidori, a high school girl who is believed to possess unique knowledge known as "Whispered," which makes her a target for various terrorist groups and rogue nations.

Sousuke, despite his exceptional combat abilities, struggles to adapt to civilian life, often causing comedic misunderstandings due to his overly militaristic behavior. His mission to protect Kaname leads to numerous encounters with hostile forces, including the terrorist organization Amalgam, which seeks to exploit the Whispered technology for its own purposes. As the series progresses, the relationship between Sousuke and Kaname evolves, with Kaname often serving as a grounding influence on Sousuke's rigid personality.

The series is divided into several arcs, each focusing on different aspects of the overarching conflict. The first season primarily introduces the characters and establishes the stakes, with Sousuke and Kaname facing off against various threats while navigating their growing bond. The second season, "Full Metal Panic? Fumoffu," shifts to a more comedic tone, focusing on Sousuke's humorous misadventures in high school without the overarching plot of the main series. The third season, "Full Metal Panic! The Second Raid," returns to the main storyline, delving deeper into the mysteries of the Whispered and the escalating conflict with Amalgam.

Key characters include Sousuke Sagara, a stoic and disciplined soldier with a tragic past; Kaname Chidori, a strong-willed and perceptive high school student who becomes central to the Whispered conspiracy; and Kurz Weber and Melissa Mao, fellow Mithril operatives who provide support and camaraderie. The antagonist, Gauron, is a recurring foe whose personal vendetta against Sousuke adds a layer of personal stakes to the conflict.

The series explores themes of war, technology, and the impact of violence on individuals, while balancing intense action sequences with moments of levity and character development. The interplay between Sousuke's military background and Kaname's civilian life creates a dynamic narrative that keeps the story engaging across its various arcs.