Will iMessage work without a SIM card?

I'm leaving the country soon for a short while and I was wondering if I take out my SIM card to avoid roaming charges and use my email instead of my number, will it still work? And will I still be charged roaming fees?

Also, will apps such as Whatsapp and BBM for iPhone work without the SIM as well?

With no sim, there's nothing to be charged to (no roaming charges). IMessage and other apps will still work but only with a Internet Connection. Hope this helped!