Question

check whether you always get a monomial when two monomials are multiplied

Answer 1

Two rules about monomials are:

A monomial multiplied by a monomial is also a monomial.A monomial multiplied by a constant is also a monomial.

Answer 2

Let the monomials be 3x and 2x
Then , 3x multiply 2x=6x2(square).
Therefore, 6x2 is a monomial