Sundar Pichai, Alphabet CEO. David Paul Morris | Bloomberg | Getty Images

Shares of internet giant Alphabet closed out the day at an all-time high on Monday as big tech companies saw gains that defied the rest of the market. Google-parent Alphabet closed up 2.7% at $1,397.81 per share, which brings the company's market cap to $964 billion. Facebook rose almost 1.9% on the day, closing at $212.60 per share, which makes the social media giant worth $606.3 billion -- a 52-week high, and just 3% off its all-time high of $218.62, set on July 25, 2018.