1Indicates that something is done skillfully, properly, or thoroughly — "well."
彼はギターをよく弾ける。
He can play the guitar well.
この靴はよくできていて丈夫だ。
These shoes are well made and sturdy.
もっとよく考えてから決めた方がいい。
You should think it over more carefully before deciding.
よく眠れば元気になる。
If you sleep well, you'll feel better.
2Indicates that something happens or is done repeatedly — "often, frequently."
週末はよく公園を散歩する。
On weekends I often go for walks in the park.
この道はよく渋滞する。
This road is often congested.
昔からよく遊んだ友達だ。
We're friends who've often played together since way back.
彼女は最近よく遅刻する。
She's been late often recently.
3Used to express gratitude or relief for something someone did — "I'm glad you...", "thank you for...".
よく無事に帰ってきてくれたね。
I'm so glad you made it back safely.
よく教えてくれました、助かります。
Thank you for telling me — that really helps.
4Used to express disbelief, indignation, or reproach at someone's words or actions — "you've got some nerve to...", "I don't know how you can...".
よくそんな失礼なことが言えますね。
I can't believe you'd say something so rude.
あんなに迷惑をかけて、よく平気な顔をしていられるね。
After causing so much trouble, I can't believe you can act so unbothered.