1. PASSIVE VOICE

2. USES To emphasis the main focus of a text or a sentence.
The company has apologised for losing details of its customers. The details were left on a train by a member of the staff.
When the agent is obvious, not important or unknown.
He has been arrested on suspicion of murder.
I hate being watched when I’m eating.
I’m sent a huge amount of spam mails.
In more formal writings (academic writing, scientific reports, news)
No survivors have been found after the hurricane.
To creat distance between the agent and the action (to avoid responsibility)
All complaints will be taken seriously.

3. FORM Use the verb to be + past participle. Maria buys some flowers.
Some flowers are bought by Maria

4. PASSIVE VOICE Active Passive Present simple
The press follows him everywhere.
He’s followed everywhere by the press.
Present continuous
The police are monitoring his s.
His s are being monitored by the police.
Past simple
Fire destroyed the building.
The building was destroyed by fire.
Present perfect
Someone has eaten my sandwich.
My sandwich has been eaten.
Will
Someone will help you.
You will be helped.
Modals
We can’t do it now.
It can’t be done now.
-ing form
I don’t like people criticising me.
I don’t like being criticised.
Infinitive with to
The organisers want people to give feedback.
The organisers want to be given feedback.

5. PASSIVE WITH 2 OBJECTS
Rewriting an active sentence with two objects in passive voice means that one of the two objects becomes the subject, the other one remains an object. Which object to transform into a subject depends on what you want to put the focus on.
Rita wrote a letter to me.
A letter was written to me by Rita.
I was written a letter by Rita.

6. IMPERSONAL PASSIVE
Verbs without an object (intransitive) normally cannot form a personal passive sentence (as there is no object that can become the subject of the passive sentence). If you want to use an intransitive verb in passive voice, you need an impersonal construction. Normally with verbs of perception (say, think, know…).
It is said that the president is going to resign.
It is thought that the crisis is becoming worse.
It is known that a hurricane is going to reach the USA.