LÖVE

Obviously when you draw a million images on a screen, it's going to lag. At least with Love2D. But how do games like Geometry Wars and Beat Hazard go about it? There's pretty much a trillion particles on the screen at times and no lag(or very little.) I'm just assuming they use really nicely animated sprites rather than use a particle system. Any advice? I'd like to get some good particles going if I can.

You can use less particles, but bigger/with more opacity.

Look into Sprite Batches.

I don't think Sprite Batches are made for always moving sprites, and anyways, I think particles systems are optimised the same way as Sprite Batches.