Science

Scientists already use SI, so no change is necessary.

Money

Our United States Dollar is already decimalized, so no change is necessary.

Nutrition Facts Label

Already in grams, so no change is necessary.

Wine & Distilled Spirits

For decades, our Wine & Distilled Spirits have already been exclusively measured in metric units (750 mL is the most common size) so no change is necessary.

Prescription Medication

Our prescriptions are already measured in metric units (mg, mL et cetera) so no change is necessary.

Military

The U.S. military uses metric measurements extensively to ensure interoperability with allied forces, particularly NATO Standardization Agreements.  Ground forces measure distances in klicks, slang for kilometers.  Most military firearms are measured in metric units, beginning with the M-14 which was introduced in 1957.  Heavy weapon caliber is measured in millimeters.  Military vehicles are generally built to metric standards.  The Navy and Air Force continue to measure distance in nautical miles and speed in knots; these units are now accepted for use with SI by the BIPM.  No change is necessary.

Weight and Height

kilograms and centimeters

Tools

We have been using metric tools for many years.  You probably have metric tools in your garage right now.

Office Paper

A4 is the most commonly used paper size in the world. Your computer printer paper tray has an adjustment to accommodate A4 which is a little taller and a little narrower than what you are used to. By 1975 so many countries were using A4 that it was established as an ISO standard, as well as the official United Nations document format.

Transportation

Just change your GPS setting to metric.  You probably already have kilometers per hour on the speedometer of your vehicle right now.

Weather

It is easy to adjust to degrees Celsius; just remember this simple little rhyme.