He decided to slide into her DMs after seeing her photo.
slide into the DMs
idiomTo confidently and coolly send a direct message to someone by means of social media, especially with romantic or sexual intentions.
Origin
first recorded 21st c.First appears c. 2011, particularly on Twitter, which allowed users to send private messages known as direct messages. The word slide suggests a smooth, confident, or subtle approach to initiating a conversation.
She was surprised when the musician she follows on Instagram decided to slide into her DMs.
Despite his usual hesitation, he gathered enough courage to slide into her DMs, hoping to initiate a conversation that might lead to a date.