Most camera manual modes have a visible meter of some sort. A needle, or a gauge, or something. A visual indication of whether the settings you have currently set are "correct" per the camera's idea of correct, and which way you need to go (more exposure or less) to get it "correct" if it's off. There might even be an indication of how far off you are.
Meter-matching on every shot is functionally identical to shooting Av or Tv, but will get you practiced with the controls. Also, some people prefer shooting this way.
More people choose to meter match, but with a picture by picture exposure compensation. They think 'I want to be 2/3 of a stop less than the camera wants' and meter-match accordingly. This is functionally identical to Av or Tv with exposure compensation, but may be more intuitive or involve fewer controls depending on the camera. Also, some people prefer shooting this way.
Lastly, some people will meter off a known target like green grass or a grey card, meter-match on THAT, and then leave the settings alone until the light changes. This gives consistent exposure over a group of pictures, regardless of whether there are a bunch of white sheep suddenly in the frame, or a bunch of guys in black uniforms, or a bright light, or whatever. Sports photographers use this a lot.