Melee

Melee weapons can only hit adjacent targets, and can only be used one at a time. Activate a melee weapon and bump (move) into a target to attack it. Other options are to left-click on the target itself, or in that target's general direction. You can also force a melee attack, generally only necessary to use a melee weapon on terrain or a machine, by holding Ctrl-Shift while moving in a certain direction. (Note to vi-key users: Forcing a melee attack using vi-keys is not possible because the commands overlap with part swapping.)

Hit Chance

Melee attacks use the same hit chance calculations as ranged combat, with a few exceptions:

 Base hit% is 70
 No range modifier
 No heat modifiers
 Utility modifiers use those applicable to melee combat

Momentum

All melee weapons benefit from greater momentum in the direction of the attack. Attacking from an adjacent space counts as having a momentum of 1, the amount of momentum gained from moving to strike a target at nearly point blank range. Moving multiple consecutive spaces in a row prior to the attack adds additional momentum, up to a maximum of 3. Current momentum is displayed as a number at the end of the HUD's movement data readout.

The damage bonus on a successful melee hit is +1~20% for non-piercing weapons, or +2~40% for piercing weapons, calculated as: ([momentum] * [speed%] / 1200) * 20. (40 instead of 20 for piercing attacks. Speed% is current speed as a percentage of average speed, 100.) Thus the more momentum and speed with which you attack, the greater the damage. Your status page shows the damage bonus taking current momentum into account.

Ramming

As a last resort, Cogmind can ram other robots to damage and/or push them out of the way. Damage is a random amount from 0 to (((10 + [mass]) / 5) + 1) * ([speed%] / 100) * [momentum], where speed% is current speed as a percentage of average speed (100) and effective momentum is a combination of both Cogmind and the target's momentum. Smashing into a robot headed straight for you can deal some serious damage, though there are serious negative consequences to go with this unarmed attack, and half as much damage is inflicted on Cogmind as well.

Impact

Impact melee weapons have a damage-equivalent chance to cause knockback, with a +/-10% per size class (T/S/M/L/H) difference between attacker and target. While incapable of a critical strike, they affect components based on relative durability rather than coverage, and are therefore effective at destroying fragile systems. Durability is calculated by inverse max integrity, so low-integrity components are considered fragile and thus more likely to take damage from an impact.

Slashing

Slashing melee weapons are generally very damaging, and can even sever components from a target without destroying them (damage/3% chance).

Piercing

Piercing melee weapons achieve critical strikes more often, and are more likely to hit a robot's core (+33% core exposure for hit location calculations).