When you think of the most iconic musical acts of all time, the foursome of George Harrison, John Lennon, Paul McCartney and Ringo Star - better known as The Beatles - undoubtedly come to mind. The Beatles were a musical inspiration for so many of today's musical acts and achieved a massive amount of success in the United States.

But what makes a band so iconic? The answer: the music. The Beatles are known for their hits - some poppy, some dark, some sophisticated - but all a part of musical lore that are still played and sung by music fans, some 40 years and counting after they were originally recorded.

Their music is inspirational and timeless - it hasn't been forgotten. And that's the mark of a great band.

Here's a look at the most popular Beatles songs, as well as the significance they maintain beyond just being quality songs:

The Beatles: I want to hold your hand

I Want to Hold Your Hand: "I Want to Hold Your Hand" is The Beatles song largely credited with helping Americans snap out of the sadness of President John F. Kennedy's assassination. They closed with the song in February of 1964 - about three months after JFK was killed - on the Ed Sullivan show, triggering a fan extravaganza. It's estimated that some 74 million viewers tuned into the program to watch The Beatles perform a set of catchy, feel-good music that was capped off with this song.

The Beatles: Let it be

Let it Be: Released in 1970, the song is inspirational and emotional, and can be perceived in a variety of ways. It holds religious symbolism and is sung with emotion to make it a fan favorite among even non-Beatles fans. It also signifies one of the final No. 1 hits the group recorded, as The Beatles broke up about a month after the song's release.

The Beatles: While my guitar gently weeps

While My Guitar Gently Weeps: For everyone who thought that the brains behind The Beatles' iconic songs were from either Lennon or McCartney, George Harrison had other thoughts with "While My Guitar Gently Weeps." The beautiful guitar playing of melodic riffs and well written lyrics make this Beatles song a fan favorite as well as serves as proof that the Beatles can branch away and make good music that isn't as poppy as some of their other hits are. Plus, The Beatles got guitar legend Eric Clapton to even lay down some riffs for the track, further cementing this song in Beatles lore.

The Beatles: I am the walrus

I Am The Walrus: Again, for everyone that thinks the The Beatles were all about the pop songs such as "Love Me Do" and "I Want to Hold Your Hand," all you need do is pick up a copy of The White Album and listen through the double disc for unusual, yet highly creative songs and music. The most notable from the album is "I Am the Walrus." It's as strange as it is good, and a popular song among the many alternative Beatles hits.

The Beatles: I saw her standing there

I Saw Her Standing There: If you've ever been to a wedding or a party with a DJ (no matter what the age demographic), chances are this song has come on at some point in the night. Chances are also that the dance floor was packed with people dancing and mouthing the words. "I Saw Her Standing There" is a poppy Beatles song, but one that's well known by anyone who knows a thing or two about music. It's catchy, it's fun and it's a fan favorite, which is why it lands on the list of most popular songs by The Beatles.

Hey Jude: The most popular Beatles song to sing along to. "Hey Jude" begins slowly and somewhat sad before launching into an outro that can have even the largest of groups of people singing together in unison. Overall, despite the sad beginning, "Hey Jude" might be one of the band's most feel-good songs. Put it on and try not to sing along with it - we dare you.

You've Got to Hide Your Love Away: This was the first song that The Beatles recorded sans any electricity in their instruments. It's still impactful, starting with lyrics sung in a monotone style, prior to a chorus that practically begs you to sing along. It's also proof that The Beatles didn't need electric guitars to make a quality song, a noted diversification in their music from many of their other songs prior to this point.

Blackbird: Blackbird is arguably the simplest of all The Beatles songs - and that's part of the reason why it's so great. Played with just an acoustic guitar, the lyrics and instrument tell the story of the song. It sounds beautiful and is also a popular nighttime song for putting toddlers and babies to sleep.

Come Together: It's all bass and drums in "Come Together" - well at least at the beginning. This song was so popular because it was so unlike anything that had ever before been done by The Beatles. And isn't that the mark of a great band? Continually experimenting with new sounds and styles so new two albums sound the same? "Come Together" was so iconic that Aerosmith covered it some years later. But their version is no match to the original.

All You Need is Love: An anthem of all love songs, both from yesterday and today. Simple, yet powerful, and the intro to the song with the repeating "La, La Love" is immediately recognized and easy to sing along to. The message is iconic and catchy.

Yesterday: "Yesterday" is arguably the most perfect ballad from The Beatles. While most of the band's songs are upbeat and poppy, "Yesterday" is slow - only played with a single acoustic guitar - and sad. It's the tale of a love gone wrong, which differs greatly from most of the band's other songs and how they depict love.