How do they make bullets in movies hitting things look so real

No one here has really explained how it actually gets done, which was the real question.
[Let’s just say for now a better question might have been: “How do movies depict seemingly realistic bullet hits and firefights? ]

How it’s usually done (summary): If the film has any decent budget at all, it’s set up by tiny explosives underneath whatever surface the hits occur. This is less the case these days in terms of body hits, but it all depends on the director too.

This picture from The Matrix Reloaded is a perfect example of traditional FX:

So you see all those holes, right? Here’s how they did this particular scene:

-Before the scene is shot the crew will drill out each “bullet hole” in the car in advance. They will also add details like the paint flaked out around the hole too to emphasize impact.
-Then they will fill it all back in with body filler, sand it all to perfection, and finally repaint it to look like a brand new Cadillac (who BTW had major product placement in the film).
-Under each of the filled holes will be a small explosive charge, each with a wire that goes to a detonator power source, which in turn is connected to a radio controlled panel or timer. Nothing is random or left to chance, both for safety and the fact that the above process is time-consuming and expensive.
-During the actual scene, each charge will go off in a preset sequence- starting from whatever side the shots appear to be fired from, adding a little randomness so it’s not too “perfect”.
-In this particular scene, during the chase scene you had a guy lean out of the other car, firing off a bunch a blanks towards this car. At the same time all the charges blow out the holes in that preset sequence and… you get a very exciting, and seemingly realistic fire-fight.

Is it really how “reality” would look? No. Does it matter, especially in a movie like this one? I’d argue: no, but you do buy that it’s at least what seems to be realistic and that’s what’s important.. Does it matter in a more realistic war movie like American Sniper or Zero Dark Thirty, which set out to tell stories that actually happened? Yes, and you’ll notice that bullet hits in those movies are not nearly so dramatic or “stagey” looking. The sound was also much more realistic.

So again, actually “real” vs “seemingly realistic” is rarely the point of a movie anyway. That’s true of all other aspects of movies as well, especially the fact that you have a soundtrack playing music over all the action! Everything is adjusted not to replicate reality, but to create an experience. They exist to tell a story, just like a book or even a song. Generally, I may prefer more realistic, or things to be closer to reality for certain stories; other times it wouldn’t make sense to even try.