I am total newbie so please bear with me.

I use guitar pro to slow down the songs to get the timing correct. So is that better then using a metronome? I don't get the point of the metronome while you play a song and you have to keep with the beat but don't the notes have different durations+ the silences so how can you play a song with a metronome?

Please help me.
Usually metronomes start counting and there will be 1 accented click or beep and 3 other non-accented click/beeps. Then repeats. This is basically telling you when a new bar is starting in 4/4 time.

Most of the songs you play are going to be in 4/4 time, maybe with a change in 1 or 2 bars. So this means in 4/4 time you can fill up a bar with 1 whole note, 2 half notes, 4 quarter notes, 8 eigth notes, or 16 sixteenth notes.

So to count those you would do this. A whole note would be 4 clicks, so you play on the accented click and hold until another accented click comes. You hold a half note 2 clicks, quarter note is 1 click, eight note is .5 clicks - Meaning you can play 2 eighth notes per click. Sixteenth notes are .25 of a beat. You can play four 16th notes per click.

Knowing that you just play accordingly, notes do get longer then a whole note, and shorter then a 16th note but those are the most commonly used notes.