Vague, but maybe Shattered Galaxy? It is/was a RTS MMORPG. If you've played Planetside 2, it has many similarities.
You customize and train up units of many types. Infantry, armor, air, and biological, but each of those classes has about a dozen different unit types, and changing equipment can completely change a unit's purpose. Mainly by changing the weapon to make a unit anti-air or anti-armor, but also there are different reactor types... I liked to bring a support vehicle with solar cells and the ability to recharge friendly units, while most units needed to recharge at gas geysers around the field.
You pick about 5-15 (depending on how you level your commander) to enter battle with. I remember seeing about 30 players total in some of the battlefields, each commanding that many units. Cooperation was very important, both for rock-paper-scissors reasons, and also to repair/heal/buff friendlies. There were three factions, plus some ineffectual native creatures who mainly existed for training purposes.
To win battles you had to capture and hold "points of control". They tended to get crowded, which is great when you focus on support units like I did. Of course, there were many artillery options available as well. I never got particularly high level, but I had a lot of fun.
Looks like it's still up and still free to play. I never put money in, but it was still fun. From what I could tell, supporting the developer wouldn't stop you from dying really quickly - it's just a fast-paced, lethal RTS. Losing units just isn't a big deal (you just have to retreat and repair them).