The structure as…as… is used to say that people or things are equal in some way.

He earns as much as his wife does.
She is as tall as her brother.
It was not as good as I expected.
She speaks English as well as the rest of us.

After not, we often use so…as, instead of as…as. This structure is more common than ‘less than’.

She is not so successful as her sister. (More common than ‘She is less successful than her sister.)

The structure as…as is often followed by an adjective or adverb.

You should get there as soon as possible.
She earns as much as necessary.

Pronouns after as
Pronouns in the objective case are used after as in an informal style.

She doesn’t earn as much as him.

You are as beautiful as her.

In a formal style, we use subject + verb after as.

She doesn’t earn as much as he does.
You are as beautiful as she is.

Note that pronouns in the nominative case (e.g. he, she, they) without a verb are unusual after as in modern English.

She doesn’t sing as well as me. OR She doesn’t sing as well as I do. (More natural than ‘She doesn’t sing as well as I.)

As much/many…as

The structure as much/many…as is used to talk about quantity.

He doesn’t earn as much money as he should.
We need as many volunteers as possible.

Tenses
In as…as clauses, we often use a present tense to refer to the future.
A past tense used after as…as often has a conditional meaning.

We will get there as soon as you do. OR We will get there as soon as you will.

As…as… in traditional expressions

As…as… is used in a number of traditional comparative expressions.

As cold as ice
As hard as nails
As black as night
As good as new