It really depends on your strategy but this guide will assume you want to exploit the power of the MEC suit as quickly as possible. Therefore, research Meld Recombination and build a Cybernetics Lab pronto.

(!) The Cybernetics Lab counts as a workshop for adjacency bonuses. Take advantage of this by building a Foundry or Workshop next to it.

Consider the way MECs are used in the early months of the game. MECs are used primarily to destroy cover and provide opportunities to attack using Collateral Damage. They can take one or two hits but generally stay out of danger by using "line of sight" to conceal them from enemy fire. Being converted from squaddies, they will have lousy aim so playing them as a straight shooter is out of the question especially since you will be using all that ammo for Collateral Damage. To reliably dish out any kind of damage, they need to be in close range.



With this in mind, the Heavy is the best candidate. The Heavy's skill, Body Shield, lowers the aim of the nearest visible alien by -20 and prevents that alien from dealing critical hits. This is the best in survivability since it applies no matter the distance as long as the alien is visible and it negates the critical chance of your typical mind-melded sectoid or thin man. Just remember not to trigger more than one group of enemies.

The Assault and Support class are tied for second. If you want to use your MEC aggressively, pick the Assault since its Shock-Absorbent Armor is handy in close quarters. The Support's Distortion Field is useful if you like to keep your MEC in the back using Collateral Damage often and leaving the mop up to the regular soldiers.

The Sniper comes in last since you do not want to use your MEC as a straight shooter. Augmenting a Sniper should be done later in the game when they have high Aim.

Your choice. The flamethrower's strength is its area-of effect. It can potentially eliminate a lot of aliens in one go which is great in the early months. The flamethrower has limited uses though and is useless against mechanical enemies like the Mechtoid and the dreaded Sectopod.



The KSM's drawback is that it can only kill one alien at a time. However, it provides a significant boost to movement range and becomes the biggest damage dealing weapon in your arsenal in the later months when fully upgraded. It makes dealing with Mechtoids and Sectopods much easier especially when coupled with the EMP ability.

The MEC has three roles.

First, the MEC is used to destroy cover with Collateral Damage allowing for flanking shots. The ability also causes minor damage that negates the HP advantage of sectoids, thin men and floaters on Impossible difficulty. It makes fighting and killing easier.

(!) Collateral Damage instantly blows up cars. Use it to kill aliens taking cover behind them.

Secondly, the MEC is used to kill enemies at close range using the flamethrower or the KSM. This is risky and requires hopping from heavy cover to heavy cover which will be explained in the later portions of this guide.

Lastly the MEC is used as a "tank" to take hits for the team. This does not mean you should rush MECs out in the line of fire. Damage should be avoided in the first place but situations may arise (often on impossible difficulty) where you know a shot is coming and it can potentially kill one of your soldiers. MECs let you mitigate damage by allowing you to decide where it goes.

Heavy Cover works differently for MECs. This should be abused as much as possible.

When a soldier takes heavy cover, it is not the tile he is occupying that's important but the tile or tiles next to him. This is because when the soldier takes a shot, he temporarily steps out to the next tile to fire and then returns to cover. He "leans" out to the next tile. As a result, any alien that can see the tile next to him can fire at him.



With the MEC it's different. The MEC is too large to "lean out". Hence, there is no "next tile" to worry about. The MEC cannot fire from heavy cover but as an advantage, the aliens cannot see the MEC. If they cannot see the MEC, they can't shoot at it.



The trick here is that even though the MEC cannot fire from heavy cover as an ordinary soldier, the MEC can still use Collateral Damage as if he could. The range of Collateral Damage is very generous. Take full advantage of this and your MEC can destroy enemy cover without even being seen!



With their cover blown, they're easy pickings.



(!) Take note that high ground can sometimes negate the concealment of heavy cover which makes thin men and floaters a problem if they get that advantage.

Heavy cover hides the MEC. Getting in range to use your flamethrower or KSM is simply a matter of moving from heavy cover to heavy cover; concealment to concealment. When done right, you should be in range to deliver the final blow easily.



In the picture above, there's not a lot of heavy cover to move up to for the flamethrower unless the MEC goes around (or through) the bus. However, more sectoids could be hiding that way. The MEC can continue hiding in heavy cover and reload for another round of Collateral Damage.

The thing to worry about when moving your MEC aggresively is triggering more alien groups. Avoid aggression when you're not sure of your surroundings. If the aliens have set an overwatch trap, weigh the risks. If aggression is not an option, you could simply use Collateral Damage or Hunker Down everyone while the MEC reloads.

Here is a hypothetical situation.

It is impossible difficulty and your team consists of three soldiers (two rookies and an Assault) and a MEC. The enemy is two groups of sectoids. It's the stupid bridge map so cover is extremely limited. Only the Assault is in heavy cover, the rest are in half cover. The MEC is concealed.

There's too many of them so the rookies do a double grenade toss. Two sectoids are dead. The Assault get's lucky and kills one. Three sectoids are left and your rookies are stuck in half cover.

You know that one sectoid will mindmeld and two will fire. The sectoids will go for the rookies. A hit could kill them and a crit most definitely will. What do you do? Move the MEC out of concealment and move it closer to the sectoids. The sectoids will definitely shoot the MEC since it has the lowest defense.

You can expect at least two shots from their plasma pistols. That won't kill the MEC. The MEC absorbs the damage the rookies cannot. The best case scenario is the mission ends with a damaged MEC but everyone alive. This is what I mean by a MEC tanking damage for the team. MECs allow you to redirect damage to a unit that can absorb it.

Medkits (fix everything) work on MECs. With a Support soldier with Field Medic and the appropriate Medal, the MEC is an efficient damage sponge.

Situations where damage is unavoidable should be avoided. Everyone Hunkering Down in heavy cover or everyone getting out of line of sight is often better. As much as possible, MECs should not have to be used this way. Just remember that the MECs high HP is a resource you can make use of.

In summation, abuse heavy cover to keep MECs hidden and use Collateral Damage to provide opportunities to kill the enemy. Move from heavy cover to heavy cover to get in position for your close range weapons. Use the MECs to absorb damage when absolutely necessary.



As always, good luck Commander!