We must invert the subject and verb in certain grammatical constructions in English: 1) In questions, with words like "so" expressing agreement, and with "should", "were", "had" in conditional clauses. 2) After adverbs or expressions like "seldom", "rarely", "only" at the start of a sentence. 3) With verbs of movement or place at the beginning, like "beyond the open fields stood...". 4) In direct speech when the subject of the introductory verb is a noun. Proper inversion is required in these specific cases.

1. INVERSION
We must invert place modal or auxiliar verb before the
subject in the following cases:
 Of course, in questions: are you walking to work today?
 With so, neither, nor to express agreement:
-I love reading.
-So do I.
 With should, were, had when they come at the
beginning of an if-clause instead of if.
Should she arrive before I come, tell her to wait.
Were I you, I would move to a new flat.
Had I known that, I would have helped.

2. INVERSION
 After the following words or expressions, when they
come at the beggining of a sentence:
Seldom do I drive during a snowstorm. But! I seldom drive
during a snowstorm.
 Only after/ by/ if/ when, not until: inversion in the main
clause. Only after he updated his skills was he able to get
a job.
Seldom
Rarely
Little
Barely
Nowhere (else)
Never (before)
Not (even) once
On no account
Only by
Only in this way
Only then
Hardly (ever)...
when
No sooner …
than
Not only … (but)
also
Not until / till
In no way
Not since
In/ under no
cirmumstances

3. INVERSION
We must invert the subject and verb in the following cases:
- After verbs of movement or advervial expressions of place
when they come at the beginning of the sentence:
Beyond the open fields stood the majestic mountains.
- In direct speech when the subject of the introductory verb is
a noun.
“I need a new computer”, Sharyl said.