わたし は Charlotte です
(Watashi wa Charlotte desu)
I am Charlotte
そら は あおい です
(Sora wa aoi desu)
The sky is blue
Is not an equivalent of the English verb 'is', and is not actually a verb at all.
The 'desu' in a Japanese sentence is not a verb but, rather, just a politeness marker. In case the sentence 'the sky is blue' sounded a little rude the first time. In the sentence sora wa aoi desu (the sky is blue) the desu isn't actually needed, unless you're trying to be polite: remarking to your boss that the sky is blue, for instance (and probably receiving a withering look for wasting time..)
The は (wa) is not a verb, either. It is a particle, marking out the sentence's topic: the sky.
So the sentence translates literally as: 'as for the sky, blue'. No verb.
This leads me to my second recent realisation about the Japanese language...
Often in Japanese, words that in English we would call adjectives behave like verbs. Yes, あおい (blue) despite being called an adjective, actually acts like a verb. The result? Here in Japan, the sky blues. My bag reds. Mountains big and a mouse smalls.
This has had little impact on my actual learning of the language so far, except perhaps a slight suspicion when my teachers insist that desu must be used in every 'otherwise' verb-less sentence. I and hundreds of others are being trained to speak such polite Japanese that, apparently, we are actually identifiable on opening our mouths, by some members of the public:
'How polite, you don't happen to go to 東京日本語学校...?'