18 months and still not talking 😩

Okay so my 18 month old just has no interest in talking at all.

He understands the words we say, like milk, juice, book, nappy etc. But he is still yet to say them.

He gets frustrated sometimes as he doesn't know how to communicate and ends up banging his head in temper on the floor, walls, toys etc.

I've literally sat in front of him repeating a single word like 'cow' over and over to see if he will copy and he never does and ends up getting upset.

Does anyone have any tips on how to get him talking?

He does say Mama and Dadda, but never in the context of wanting our attention, just saying it because he can and we might possibly be on his mind.