I guess you should change your moniker to audiodummy
Most people shooting video do not pay attention to audio and it is really important. One reason they don't is that on most cameras there is agc - auto gain control. What it does is to ensure no matter what the sound level actually is it is recorded at one high level. It thus never overloads, but there are no dynamics whatsoever. In a quiet room you hear a lot of noise as the agc pumps up the naturally low sounds to be at that high level for the recording.
OK, so why do we care? Well if you are recording a voice (talking head), the agc may pump up the background noise between sentence pauses - very unnatural. If one is recording classical music, you lose all the dynamics that are part of that genre (you know, pianissimo, crescendo, etc.).
Now if you are recording an amplified rock band, all their music is already gain controlled to be always loud. For that agc is fine as it will prevent overload (unless the mic is overloaded). There are no dynamics. it is just loud. (There may be a gain switch on the mic, check that out).
So, first you have to decide whether you want to continue with agc. If not, then using an internal or external mic, you turn off the agc (the camera audio controls affect both the internal mic or the mic that is plugged in). You then have to choose the audio level manually. And what that setting is depends on, guess what? - what you are recording and how far you are from the source. The camera has meters to guide you - you want the loudest sound to reach -6db and never go in the red. If it does, you get some ugly, nasty noise. If you record too low, the signal-noise ratio will be poor. It is hard to do audio recording.
Which is why most people don't bother to turn off agc.
And, btw, recording anything with the mic on the camera is a really bad idea - you want the mic near the source not the camera. But that is hard to do.