Shoulder
The shoulders express strength and power, as in the term "broad-shouldered." The shoulder is required for using the arms (see this); if one injures one's shoulder, one can no longer control one's arm; cannot work, carry anything, and so forth. We also use the expression "to shoulder" something when we take on a job or accept responsibility. In a Gnostic text, it is stated that "Jesus is called the shoulders of the seed"; an early theologian wrote that "the shoulders ... denote the ability to create, strive, and accomplish," etc.
Relationship
On the other hand, shoulders in dreams can symbolize relationships – giving someone an appreciative pat on the shoulder, lifting a child or a girlfriend onto one’s shoulders, crying on someone’s shoulder, placing an arm around someone’s shoulders in camaraderie, and so on. So if this occurs in the dream – or if the gesture is rejected – it is likely more about relationships, eros, than about strength. One always needs to understand a symbol in its context.