Usage in battles

The multiple cannons allow for different combinations of attack. The 37 mm gun on the full 360° traverse turret allows for a diverse role on the M3, with its high-velocity and effective round for long-range fighting, but with a fast reload for close-quarter encounters. The 75 mm on the sponson mount has the same penetration level as the 37 mm, but with a very high post-penetration damage with the right ammo at the cost of lower velocity, and thus a shorter battle range. The limited traverse on the 75 mm mount also means it is not as flexible as the turreted 37 mm. With these two cannon, the M3 Lee can focus on close-range combat with the two cannons fighting a single tank or engage two separate tanks at a longer range. Closer range combat is supported by the M3's adequate sloped frontal armour, able to withstand most enemy fire at its battle rating. It is recommended to set the keys to allow separate firing of the cannons for maximum effectiveness.

Still, different guns mean different styles of play. The M3 can also play as a tank destroyer, using its sponson gun to take shots at medium range and it's 37 mm to cover the flanks and make longer range snipe shots. The M3 Lee can also be used as an assault tank, quickly advancing on points while switching between the powerful 75 mm gun and the faster-firing 37 mm. It is also possible to completely ignore the 37 mm and focus solely on the 75 mm as it is a far more effective gun with its HE filler in its APCBC, as well as being easier to manage for newer players. In all game modes, the weapons should be assigned to different keys, this will allow the tank to aim using the sights of the three guns separately, allowing more accurate targeting at ranges, especially for the 75 mm gun. Since the 75 mm is in a side sponson, it is also possible to approach cover to where only the 37 mm is showing, allowing the tank to fire with most of the tank's profile hidden.

Being at BR 2.7, the M3 Lee has a possibility of facing long-barrelled Pz.Kpfw. III, and Pz.Kpfw. IV, as well as T-34s, and (rarely) the Chi-Nu II. The ZiS-30 is also very deadly, as its gun is competitive even at 5.7. The 75 mm gun can reliable penetrate all of these tanks at short range (save the T-34), whereas the 37 mm will require some particular shot placement.