Magneto has an army of 1,000 ten story tall Sentinels. All of them are directly linked to Magneto. Needless to say, Magneto acts as the central processing unit for the entire collective of Sentinels. Magneto is not only acting as the central unit of the collective, but he is also acting as the battery. Therefore, the Sentinels are enhanced. Multi-phasic shieldings, reinforced armor, automatic regeneration, multi-phasic disruptor beams along with both nuclear powered and anti-mattered powered missiles (2 of each per Sentinel). Each of the Sentinels are capable of traveling and maneuvering at sub light speeds because Magneto upgraded their thruster booster rockets under their feet with impulse powered propulsion systems.
Magneto himself, will be the background operator. And will be fully powered and at his prime. He will be escorted by four tri-Sentinels at all times and his forcefield will be on at all times. Moreover, his forcefields will be in rotation constantly with random frequencies per second. Aside able to control the collective at free will, he is able to aid them by interacting with the battle against the Borg; Meaning he can use his powers to attack the Cube all the while, repair broken or destroyed Sentinels.
The Borg: There is only one (1) Borg Cube; however, there are more on their way. A Tactical Borg Sphere and two other Cubes. They are using a Trans-Warped conduit to travel from the Delta Quadrant to Magneto's Asteroid M. The question is... Can Magneto defeat and program the Cube to have the others alter course before they reach the battle? Or... Will Magneto and his technological and biological components be assimilated within the Borg Collective?
P.S: While the Borg are fighting, they are assimilating data from both Sentinels and Magneto. So in case any of you are thinking that Magneto can "easily" penetrate through the Cube's central matrix. Be advised that the Borg are also compensating their efforts with rotating the frequency of their dampening field.