Formal:
* The lawyer was insistent that the witness provide further details.
* The company's CEO was insistent on a more aggressive marketing strategy.
* Despite the evidence, the defendant remained insistent on his innocence.
Informal:
* The toddler was insistent on having another cookie, even after he'd eaten three already.
* My friend was insistent that we go to the concert, even though I wasn't really interested.
* The rain was insistent, drumming on the roof and preventing us from leaving the house.
Figurative:
* The insistent chirping of the birds outside my window woke me up before dawn.
* The insistent beat of the music urged the dancers to move their feet.
* The insistent memory of that day kept returning to haunt her.
You can also use "insistent" to describe a person or thing:
* She was an insistent personality, always pushing for what she wanted.
* The insistent ringing of the phone finally roused him from his sleep.
Remember that "insistent" conveys a strong sense of urgency or determination. It emphasizes that someone or something is not giving up easily.