Function:
Arms are necessary for various body movements like lifting, pulling, pushing. You can carry loads by your arms.
Diseases:
Arm pain may be because of muscle strain or sprain, faulty posture which causes the stress on the arm resulting in arm pain; deltoid abscess also results in arm pain.
Interesting facts:
Humerus the upper arm bone is jokingly called as the funny bone. The injections are mostly given in the deltoid muscle of the arm.