Drone grasping on power lines for recharging is challenging since it requires the gripper to be lightweight, carried by a drone, and efficient for a firm grasp. A deep understanding of the power line nature and its magnetic characteristic helps ease such challenges and bring new knowledge to gripper design. In this work, a novel adaptive, lightweight, and fail-safe magnetic gripper with a recharging feature is presented. The gripper exploits the radiated magnetic field of the lines for charging and holding the drone and can easily detach from the line. The gripper design has been validated in the lab and on a quadcopter with a real power line.