Answer:
Yes and no. Groups on the far left are all definitely metals. Similarly - far right are non metals. As you get closer to the middle there are things like semiconductors. It happens on the first row of 8. Beryllium is definitely a metal. Boron is sort of in-between and carbon is a non-metal even though graphite is conductive.
The transition elements are often referred to as transition metals because they generally have one or two loosely attached valence/conduction band electrons, although there are 1 or 2 exceptions as the elements get very heavy.
