I mean just like imperial, the units are based on SI which is mostly metric. Anything SI with distance can and is defined in meters. It’s just that using meters to convey such quickly gets messy since the universe isn’t going to make everything near round numbers. To give you a fermi approx of an AU, light takes 498 seconds to reach earth, light travels at 2.998x10^8 meters/second, therefore 1 AU is approximately 1.5x10^11 meters, that’s 150 gigameters, note the earth is only 40 mega meters even by the original meter definition.