This is the 164th most frequent Arabic word.
سيكون
"سيكون" means "will be."
Here 'سيكون' is used as a future tense helping verb to indicate that the state described ('جميلاً') will occur in the future.
سيكون الطقس جميلاً غداً.
The weather will be beautiful tomorrow.
Here, 'سيكون' denotes a predicted emotional state ('سعيداً جداً') that someone will experience in the future.
إنه سيكون سعيداً جداً عند رؤية أصدقائه.
He will be very happy to see his friends.
In this sentence, 'سيكون' is implying an obligation or necessity to perform the action in the future, as described by the phrase 'علينا العمل'.