i hear all the time when somebody plays the guitar, they play the melody with the chords too. sometimes the chords sound like an actual one note that fits into the song. other times it just makes the song more interesting.
how do you play both
a trick they use sometimes is they play the chord and hold it there and they pick the notes out of the chord. so if you can kinda get what i mean they grab a chord and strum it, but they keep the chord and play notes out of it.
but usually they have two different guitars playing or the same guitar with both parts recorded separately and later synced together.