Creating bootable media from an ISO image.
It is recommended to write the image on the drive as-is, due to the simplicity and universal availability of this method. This will irrevocably delete all data on the drive and overwrite everything by the image, starting from physical block #0, including any partition tables and file system metadata. No additional setup is required, as ISO images typically contain the Master Boot Record boot sector themselves (which gets written to the disk), and are therefore considered “bootable”.
Erasing the disk before writing the ISO is unnecessary, unless you need to give the bootable media to someone else and/or otherwise need to ensure that any data that used to be on the disk is definitely erased.
“BEWARE, for all who don't verify their device IDs before using it as an output of dd, are subject to the whims of fate. Make sure that when you pass /dev/sdX to any command that writes to it, it is exactly the device you believe it to be, so that you don't accidentally wipe your system.”
First, identify the device. List your devices with ls /dev before and after plugging in the storage media, and compare the outputs. Choose the identifier of the device itself, which is the one in its topmost/simplest form. Typically, it should be sdX on Linux, and diskX on macOS, where X is a number. Additionally, on macOS you may use the rdiskX device — the r stands for raw mode which makes the transfer significantly faster.
Devices are normally auto-mounted, and should be unmounted (not ejected) before writing to them. Use umount /dev/<ID> on Linux and diskutil unmountDisk /dev/<ID> on macOS.
The ISO image may now be copied to the device, typically with cp or dd.
dd if=<ISO_PATH> of=/dev/<ID> bs=4M
After completion, macOS may complain that “The disk you inserted was not readable by this computer” — select “Ignore”. The device should now be bootable. Eject it with eject /dev/<ID> or diskutil eject /dev/<ID> on Linux and macOS respectively.