The verb ser is conjugated accordingly:
yo: soy
tu: eres
el/ella/usted: es
nosotros: somos
vosotros: sois
ellos/ellas/ustedes: son
Two circumstances are when describing your job/occupation and describing anything in general.
Here are two of the four letter words utilizing those 4 letters in a combination that immediately come to mind.
1. grin
2. ring