This key will fit the lock.

To be suitable or appropriate for a particular purpose or situation.
This shirt fits me well.
Does this key fit the door?
The puzzle pieces fit together.
fit for purpose
fit in
fit out
suit
match
be appropriate
Please fit the new key into the lock.

To adjust or adapt to a particular condition or requirement.
This key fits the old lock.
We will fit the new parts.
He fits the mold perfectly.
fit for purpose
fit in
fit out
suit
adapt
match
This shirt fits me perfectly.

To be the correct size or shape for someone or something.
Does this dress fit you?
The key will fit the lock.
My shoes fit well now.
fit perfectly
fit well
fit the size
suit
match
conform