Can entities have associative links between themselves, or is it necessary to use an aggregate for such a case?

Question

Problem-Based Design

I apologize in advance for my poor knowledge in the field of DDD. If I'm wrong somewhere, please correct me.

There are entities: ORDER, PAYMENT_METHOD

In the ORDER entity there is a reference to the identifier of PAYMENT_METHOD (many-to-one relationship).

Can there be a full-fledged associative relationship between the ORDER and PAYMENT_METHOD objects, that is, in the ORDER entity there will be a method that returns the PAYMENT_METHOD object, or is it necessary to use an aggregate for this?