The Passive: Future and progressive forms

ACTIVE: Tom will write the letter tomorrow.
PASSIVE: The letter will be written tomorrow. (by Tom)

If your passive sentence has a necessary "by" in it, it is likely that the active form is better.
The passive is used when the person (agent) is not very important - what happened is more important than who did it: The BY + AGENT is usually omitted in the passive sentence.

An exception to this is for works of creation where we DO use the passive - for no good reason, that's how it is! So phrases like the following are perfectly normal:

"Hamlet" was written by Shakespeare.
"St. Pauls" was designed by Christopher Wren.
"The Haywain" was painted by Constable.

Earlier activities look at the present and past passives. Here are examples of other tenses:

Examples: ACTIVE:

Future:
WILL THEY pay the bill in cash?
They WILL PAY the bill in cash.
They WON'T PAY the bill in cash.

Present Progressive:
IS the secretary FILING the documents?
The secretary IS FILING the documents.
The secretary ISN'T FILING the documents.

Past Progressive:
WAS ANYONE REPAIRINGthe road outside the house when you left home this morning?
Yes. Someone WAS REPAIRING it when I left home.
No. They WEREN'T REPAIRING it then.

"Going to" future:
IS the company GOING TO PROMOTE Peter?
Yes. They ARE GOING TO PROMOTE him.
No. They AREN'T GOING TO PROMOTE HIM

PASSIVE:

Future:
WILL the bill BE PAID in cash?
The bill WILL BE PAID in cash.
The bill WON'T BE PAID in cash.

Present Progressive:
ARE the documents BEING FILED?
The documents ARE BEING FILED.
The documents AREN'T BEING FILED.

Past Progressive:
WAS the road BEING REPAIRED when you left home this morning?
Yes. It WAS BEING REPAIRED when I left home.
No. IT WASN'T BEING REPAIRED then.

"Going to" future:
IS Peter GOING TO BE PROMOTED?
Yes. He IS GOING TO BE PROMOTED.
No. He ISN'T GOING TO BE PROMOTED.