The planet closest to the Moon is almost never the same one. It changes all the time, just like your best friend on a road trip might switch seats every few hours. Because the Moon orbits Earth, and Earth orbits the Sun, the lineup of planets near it keeps shifting.
Right now, the closest planet to the Moon is usually Venus or Jupiter, depending on the time of year. But if you catch it at just the right moment, Mars or even Saturn can sneak in for a visit.
Think of it like this: imagine the Moon is the cool kid in the schoolyard, and the planets are its friends who come over to chat. Sometimes Venus leans in close, other times Jupiter hovers nearby. The answer is always a friendly "it depends."