One cannot really not answer this question because no two rainwater samples will ever be the same. In fact, if we collect multiple samples of rainwater at the same location, just over a broad time span, the samples will all be different.
Water is the universal solvent, so rain will, in fact, absorb contaminants from the atmosphere as it falls. If the contaminants are harmful, then the rain may indeed have toxic levels of metals in them. However, in some areas of the world, air quality is very high so the rainwater is also pretty clean.
Also remember that as rain falls it actually does absorb contaminants and by friction, scrub the air. We will find that the chemistry of rain at the beginning of a cloud burst high in contaminants, while the chemistry after two hours is much better; that being because the previous rain eliminated a lot of the contaminants in the air.
Our altitude will also have an impact on the quality of the rainwater we are drinking. The less time/distance the rain has to fall to get to us, the less contact time it has with contaminants so the cleaner it will be.
If there is lightening, the released ozone will oxidize a lot of the organic and biological contaminants in the air. Of course as we are looking up, mouth agape catching raindrops, we might get blasted by lightening. In that case, rain is very dangerous to drink!
In most parts of the US, rainwater is safe to lap up some drops as it falls. But catching glasses of it for drinking? The truth is that it won’t likely taste very good. Also remember, that rainwater does not have chlorine in it, so if the water sits for any length of time, bacteria, viruses, algae, fungi, and God knows what else are likely to start growing inside of it.