#to join

• To adhere — To stick, cleave, or remain closely united to a surface through molecular attraction forces or structural friction; figuratively, to become a partisan of an idea, to register or become a member of an organization, a party, or an international treaty, fully sharing their principles and objectives.
• Attach — To join or to become closely joined by means of an adhesive substance, by pressing, welding, or sewing; to add a structural element to an already existing assembly to form a unified whole. In a figurative or social sense, it refers to a person joining a group, intimately adhering to a cause or an idea, or developing a deep emotional attachment to someone.