Metal Slug is a run and gun action shooting game. In order to finish each level, you should continuously shoot at the incoming enemies. At the end, you will face the boss, who is much bigger and tougher than the smaller enemies you faced throughout the level. Once you defeat the boss, you win the level and will move on to the next.
Find weapon upgrades and Slug tanks to use in the combat. Attack your enemies with a knife (a melee attack). Extra items can be found in the scenery (which you can destroy to retrieve these items and powerups). When POWs (Prisoners Of War) are freed, they offer the player random items and weapons. Metal Slug features 6 levels (each in different settings) and enemies, who have mechanized means of attacking you (like tanks, aircraft and so on).
Use the arrow keys to move your character, ‘J’ to shoot, ‘K’ to jump and ‘L’ to Grenade. Make it through each level, facing and killing off incoming enemies. At the end of the level, before you reach the exit, you will have to face the boss, who is stronger and larger than any of the enemies you faced in that level. Once you defeat the boss, you can make your way to the next level. However, if the enemies attack you enough, you will lose that level.