Modal conjunctions belong to the subordinate conjunctions. They always have an adverb of manner. A few examples are: conforme, según, de acuerdo con, de manera que, de modo que, etc.

Let's look at some example sentences.

Ella está estudiando conforme lee el libro.
She is studying as she reads the book.

Es una cepa cuyo sabor varía según la cosecha.
It is a vine whose flavor varies from harvest to harvest.

La escuela sitúa a todos los alumnos de acuerdo con sus notas.
The school places all the students according to their grades.

Olvidó el número de teléfono, de manera que no pudo llamar.
He forgot the phone number, so he couldn't call.

Lucía lavó el carro, de modo que está limpio.
Lucía washed the car, so it is clean.