welcome to the party有“欢迎参加聚会”的意思，还可以表达现在你总算懂了。

【例句】
Welcome to the party, your brain is really slow to react.
现在你总算懂了，脑子反应真慢。

Welcome to the party tonight. It really means a lot.
欢迎来参加今晚的晚会，这是一个很有意义的晚会。