Word order in English sentence!

[Martina Durisova]

I am a little bit confused of the word order. I learnt at school that the basic word order of English sentence is a subject, a verb, an object. Each English sentence always must have a subject. But I have some sentences where it does not stand.
The text is from a shortened version of the book Frankenstein by Mary SHELLY:
" A man was sitting on the ice and near him was a broken sledge."- I was taught that the missing subject should be replaced by there. Near him should be an adverb of place.
Another example:
"There was a wild storm, and with it came the most frightening thunder and lightning that I have ever seen in my life." Is the word order of the underline sentence acceptable? Where is the subject?
"About twenty metres in front of our house was a great tree." In this sentence there is not a subject too, I think.

Could you help me and explained it to me, please?
Thank you very much

[SoothingDave]

Sometimes, for effect, the subject and verb are inverted in order. "A great tree was about 20 meters in front of our house" is the "normal" order.