Metal Slug is a popular video game franchise that was first released in 1996. The games are side-scrolling shooters, where players control soldiers who fight their way through enemy forces to complete missions and rescue hostages. The main character, known as the Metal Slug, is an armored vehicle that can be piloted by the player or used as a stationary weapon. Overall, the phrase "metal slug" refers to both the game series itself and the titular vehicle/weapon featured in it.