The primary function of a microcontroller in electronics is to serve as a compact integrated circuit that governs a device's specific operations. It contains a processor, memory, and programmable input/output peripherals that enable it to perform tasks autonomously. Microcontrollers are used in various applications, from home appliances to automotive systems, controlling functions based on input from sensors and delivering outputs accordingly. Their programmability allows them to be tailored for specific applications, thereby enhancing the functionality and efficiency of electronic devices.