Not always. There are LMIA exempt categories based on various factors such as the job category, your country of citizenship, etc. To know more, refer LMIA Exempt work permits section.
Depending on your country of citizenship, you may need a TRV or an eTA to work in Canada. however, if you are a citizen of the USA, you need neither of these.
An open work permit allows you to work for any Canadian employer. To know more, click here.