Can I connect my microsoft surface to my Imac and use it as a monitor?

You might want to ask this question on the Microsoft Surface forums.

My guess would be no.

Apple, usually, doesn't design and make their devices and computers to interface with competitors' mobile devices and computers.

Good Luck!

there is software which let you do it wirelessly like air display from avatron and I'm sure many others but there would likely be a input lag and it would likely be software they would charge you for

The only way would be with Microsoft Remote Desktop via

WiFi which is available in the MacApp Store.

No way to do a physical connection, period!