You could do the tech stuff in metric but the personal stuff in imperial.
Height measurement and weight of a person, body and room temperature should be in imperial, or the imperial numbers / units mentioned, those are not intuitive, and if you want to set things like a person is short and overweight by stating the numbers you will need to go imperial.
Travel distances such as walking, car travel, or like modes is better in miles, but KM also works. Elevation (above sea level, or accent of a mountain M can work, but feet may be better for the US. Spaceship travel in KM is fine.
If you chose to go metric, there are several ways to do it, like the person was brought up in metric from an immigrant or foreign family, from another country, or they have a passion for it they got from a school teacher in 7th grade, or their used car has it as it was bought from Canada, or a grey market new car. If you do, perhaps the reader can explain the conversion when it matters. If they live in another country altogether that is also a good reason for it. If they are metric by country, you can slip in the opposite, that they are interested in the imperial measurements and will put in both as part of the thought process, or even they are trying to learn imperial so explain the thoughts that go through their mind, or have a friend character who they will translate for understanding.
Another option is to use an archaic unit, or make up one if it’s a future setting or steampunk.