Greg REFUSED to pay for the meal. We use "refuse" because it is the opposite of accept. The SCRAP metal dealer... I use "scrap" because that is what we use in my area of the US and it just sounds better to me. However, "waste" could be correct as well.

Greg REFUSED|DENIED to pay for the meal as it was to disgusting to eat. It seems that the both variants are correct. What is the difference? --> You could say both, but "refused" sounds more natural here. The REMNANT|LEFTOVER|SCRAP|WASTE metal dealer went around the houses collecting broken machines that people didn't want any more. OMG, I even cannot choose 2 words o_O -->"Scrap metal" is the most appropriate term here.

Refused and Scrap