"He looks for a job."
Translation:Il cherche un emploi.
No, because here we're talking about looking for a way to be paid for your work. "métier" designates the profession, what kind of work the person is doing.
For example if you say "Je suis avocat" ("I'm a lawyer"), you're telling what "metier" you're doing.
But if you want to change the word "emploi" in this sentence, you could use "travail" instead.
I remember poste and boulough a lot in informal conversation. On cherche du boulot. On cherche une poste. Are these unnatural or inappropriate? Are they a particularly casual way to put it?
"boulot" is a familiar synonym for "emploi" or "travail".
"poste" could work as well, but is slightly different, because it designates a position.
And "boulough" doesn't exist.
métier = trade, occupation, job, skill, experience. http://www.larousse.fr/dictionnaires/francais-anglais/m%C3%A9tier/50887 Examples: Je suis violoniste de métier mais je travaille dans la restauration et mon lieu de travail est McDonald's. Il est ingénieur de métier, mais en ce moment il enseigne les maths = He is a professional engineer, but he currently teaches math(s).
travail = work, occupation, job, (hard) work, , post, labor/labour, (piece of) work. http://www.larousse.fr/dictionnaires/francais-anglais/travail/78326 Example: réparer ce jouet est un travail délicat = repairing this toy is delicate work
emploi = job (sans emploi = unemployed, out of a job) http://www.larousse.fr/dictionnaires/francais-anglais/emploi/28832. Example: le marché de l'emploi = the job/labour/employment market.
"Métier" really has more to do with one's area of expertise, your skill set, your trade, your craft. "Emploi" is what you do to get paid.
"Il cherche l'emploi" I suppose would mean "He's looking for employment" which is technically not right in this case, but is frequently used.