It’s rare for a game series to remain popular even as it changes flavor over seven titles. But the Metal Slug series has succeeded. The timeless series feels just as at home in today’s retro indie scene as it did in the era of the original.

So let’s take a look at the Metal Slug series and how it beat out the competition.

Metal…Slug?!

The original Metal Slug was an indirect descendant of several games from development studio Irem, who had already had success with titles like R-Type, In the Hunt, and Gunforce.

Metal Slug is the child of the latter two, developed by an immigrant from Irem in the form of a new studio, Nazca Corporation. The wild shooter style of the team’s previous titles combined with lessons learned during development to create a final product of purely distilled and perfect game design. This gameplay is presented in a now iconic and timeless aesthetic, making Metal Slug arguably one of the most complete packages in gaming.

The series’ odd name comes from its eponymous mascot weapon, the Metal Slug Tank (in a strange connection to the similarly named Metal Gear series). This was originally intended to be the main player-controlled unit before the game was revised to include human characters. The Metal Slug is still present as a vehicle in the original game, and was later joined by various other player vehicles, also called Slugs.

The original game was released in 1996 on Neo Geo arcade software and home consoles, but was also ported to various other platforms in the 90s.

Metal Slug’s graphic style and art design are so amazing that it still holds up today as if it were an indie game made in a retro style. Metal Slug’s aesthetic is instantly recognizable with its chunky, bulbous look, giving even its mechanized infantry organic curves and bulges. Some bosses and enemy machines have very intricate designs and are a joy to fight. It’s no surprise that the series has stayed true to this aesthetic through multiple iterations.

The original Metal Slug was a hugely successful commercially and professional title, and was followed by Metal Slug 2 in 1998 and Metal Slug 3 in 2000, but not before series creator Nazca merged with SNK. Among other improvements and additions, Metal Slug 2 introduced character changes to the series; characters could become mummified or obese, and the controls changed dramatically. Metal Slug 2 was later remastered as the definitive edition, Metal Slug X, and released the following year.

Metal Slug 3’s major contribution to the series was the introduction of branching paths, which increased the game’s replayability. For many, Metal Slug 3 is the pinnacle of the series, the perfect essence of everything that makes Metal Slug great.

Feeling Sluggish

In the early 2000s, SNK fell into dire financial difficulties, eventually filing for bankruptcy and being forced to sell the rights to several in-house IPs, including the Metal Slug series. Developers Mega Enterprises and Noise Factory acquired the rights to Metal Slug and developed Metal Slug 4 as the first game in the series.

Metal Slug 4 didn’t take any big risks and stuck closely to the series founder’s formula, except that it added a scoring system that counted the number of enemies killed in a certain amount of time, and also included new transformations and several new vehicles.

Metal Slug 4 received mostly good reviews, and mainly demonstrated that new developers could repeat the success of older developers. However, it remains the only game developed between SNK’s collapse and its rebirth as Playmore Corporation (later renamed SNK Playmore).

After SNK Playmore reacquired the rights to Metal Slug, the company returned to chair development for Metal Slug 6. Leaving the Neo Geo behind, this version was developed for the Sammy Atomiswave arcade platform and ported to the PlayStation 2 the same year.

Metal Slug 6 continued the story of the Rebels and Martians from Metal Slug 3. Metal Slug 6 introduced two difficulty levels, with easy mode giving the player increased firepower but resulting in an early end to the game. As always, many new vehicles appeared alongside the old classic vehicles, and each character now had access to character-specific abilities. It may not sound revolutionary, but this was the first Metal Slug to introduce weapon switching, allowing players to carry multiple weapons at once.

The Future is Now

The latest installment in the main series was released in 2008. Metal Slug 7 was again developed by SNK Playmore and was developed for handheld devices and released on the Nintendo DS.

Metal Slug 7 took advantage of the dual screens of the DS and introduced a touchscreen level map, allowing players to see an overview of their current level and navigate it, putting more information at their fingertips than in previous titles.

A remake of the game, Metal Slug XX, was later developed for the PlayStation Portable and released on Xbox Live Arcade. This version revised and expanded 7, notably increasing the game’s replay value and including branching paths reminiscent of the changes introduced in Metal Slug 3.

This is the end of the main series, but the spinoffs, compilations, and remakes are worth investing your time into. We won’t go into too much detail here, but Metal Slug has had its share of handheld and mobile games, with the latter having a particularly mixed record. There are over 30 games in total in the larger Metal Slug series.

The main Metal Slug series hasn’t had a new release since Metal Slug 7 in 2008. Like its distant ancestor R-Type, Metal Slug belongs to an underrated genre in modern gaming. A 2D arcade-focused shooter that bears little resemblance to games like Call of Duty or Battlefield, Respawn’s Titanfall does hint at over-the-top action and ridiculous vehicles.

Players looking for a new Metal Slug are more likely to find it in the indie scene, with games ranging from Cuphead to direct descendants like Blazing Chrome. Games from the original era of Metal Slug can also be found in various retro collections.
Metal Slug didn’t offer any radical innovations, but the game still has plenty of ammo. The Neo Geo arcade brand has recently seen a resurgence with the Neo Geo X, and SNK has already announced that the release of Neo Geo 2 is on the way. Metal Slug 8 would be a natural partner for the platform, potentially ushering in some sleek, stylized warfare after a decade of relative peace.