Seismic isolation technology is an effective means to improve the seismic performance of buildings and important equipment. However, the seismic isolation of tall flexible electrical equipment remains challenging due to the strict requirements of a large tensile capacity and self-centering ability. In this study, a modular metal seismic isolation bearing (MMSIB) is proposed. The MMSIB is composed of steel plates, linear guides and sliders, springs, and friction dampers. The linear guide rails are used to restrict the direction of movement and prevent the overturning of the MMSIB, and the springs are used to adjust the horizontal stiffness of the MMSIB and provide self-centering ability through pre-tension. The friction dampers are used to control horizontal deformations of the MMSIB with adjustable energy dissipation ability. The effectiveness of the MMSIB is verified via a shaking table test of a 110 kV current transformer (CT). The results show that the MMSIB exhibits excellent isolation performance. The acceleration response at the top of the CT is found to be reduced to 7.32%-32.57% of that of the non-isolated specimen. The MMSIB can provide sufficient anti-overturning ability that satisfies the requirement of the inter-layer seismic isolation of electrical equipment with supports. The MMSIB has good self-centering ability with limited residual deformation that is less than the reference value.