All muscles do a single action, they contract and relax. Your body has different chores for the muscles to do.
Skeletal muscles move and support bones.
Skeletal muscle fibers are elongated cylinders containing several nuclei. Much larger than other types of muscle fiber, many skeletal muscle fibers are visible to the naked eye. Individual fibers can extend the entire length of the muscle. The firm white tendons form a core for the red muscle by extending far inside its mass and emerging at the ends of the muscle to link it to bone. Muscle fibers and tendon fibers are completely different materials and do not merge.